In an official announcement, Swire Properties said it sold the first 6,755 sq ft flat on the eighth floor of Opus for HK$430 million, or HK$63,657 per sq ft - substantially less than had been reported, and certainly no record.

The most expensive flat, in terms of price per sq ft, was sold last year by Henderson Land at 39 Conduit Road for just under HK$64,000 per sq ft. A duplex in the complex was leased for HK$1.25 million a month.

The Opus incident exemplifies the information asymmetry that characterises Hong Kong's property market. Not that it's difficult to fathom why the market continues to sizzle. Ingredients such as excess liquidity, tight supply and low interest rates are themselves enough to keep the market on the boil. The absence of a mechanism to protect buyers from potentially biased information only adds to the heady mix.

In the Opus case, for example, no one knows where the initial information came from and how it spread. But the stories did their job, starting a self-fulfilling spiral of more "record" deals in the following days. The next day, in fact, a 2,980 sq ft flat at 8 Peak Road was reported to have been sold for HK$86 million, or HK$29,000 per sq ft, a record for that project.

"One week is a long time for smart dealmakers," said John Siu, executive director of property consultant Cushman & Wakefield, indicating that those looking to make a quick buck took full advantage of the hype generated by the false information to flip homes and whip up even more frenzy.

The frenzy after the Opus news could easily have been avoided had a clarification been issued right away, he said.

The Opus incident prompted the Estate Agents Authority to launch an investigation into the episode, and Swire Properties promised to co-operate fully.

In a written reply to questions posed by the Swire Properties said: "We never comment on speculative comment over which we have no control as to source or content. We do not create false or misleading rumours. We make formal announcements as soon as we have something factual and of substance to say. In the case of the Opus, we issued a press release very shortly after we completed the deal."

The incident nevertheless raises some serious questions for an industry that drives a large proportion of the city's economy. How accurate is the available information on property transactions? Can homebuyers take this information at its face value and base their decisions on it? Does the government have a duty to provide information, which is currently mostly sourced from property agencies themselves and naturally carry an implicit risk of being skewed?

"Exaggerated reports certainly add fuel to the fire," said Lawrence Poon Wing-cheung, a spokesman for the Institute of Surveyors' housing panel.

At the moment, all property transaction data generally comes from the two largest real estate agencies in the city - Centaline Property Agency and Midland Realty. And, the numbers they are currently flashing are enough to send any property investor scampering to the nearest sales office of developers.

In August, more than 40 home transactions were completed at record prices, up sharply from only 15 in July, according to Centaline, which has about a 40 per cent share of Hong Kong's property brokering market.

"That should be the largest number of record-breaking deals in a month in the past 10 years," said Midland Realty director Sammy Po Siu-ming, an industry veteran of more than 20 years.

As most homeowners have raised their asking prices and refuse to sell, the number of "record" deals has come down somewhat this month.

Extracting information from Centaline's website about housing prices is fairly easy. Its website allows anyone to check the latest transaction prices in 100 housing estates across Hong Kong - from new developments such as the one-year-old Lohas Park in Tseung Kwan O to the 40-year-old Wing Tak Building in Wan Chai - that it tracks closely through its 300-plus branches. The range of data available on Centaline's site is impressive, and by extension, convincing.

Centaline also regularly posts cheerful property stories. Two records were set recently in Tai Po's Beautiful Garden in just one day and 13 flats changed hands in a day in Taikoo Shing, making it the busiest day in property transactions since the 1997 peak. Some of these deals broke the record HK$12,000 per sq ft price in Taikoo Shing.

Midland Realty, Centaline's biggest rival, has reported fewer "record" deals, reporting only eight such transactions in August, one in July, two last month and six this month.

At present, homebuyers simply have no choice but to rely on information compiled and fed by Centaline and Midland. This over-reliance is the result of an antiquated and inefficient government information service.

Registration of property purchase and sale agreements generally takes about four weeks before they show up in the Land Registry records that the public can browse. Home seekers thus rely heavily on information from realtors to judge the market mood.

Louis Chan Wing-kit, Centaline managing director (residential) for Asia-Pacific, said the firm's website only reports transactions handled by its agents and does not register unverified transactions.

"Our frontline sales are reported to the branch heads after the deals are closed. The details are then encoded into our central data system in about seven to eight days. Then everyone can go to our website to check information such as transaction prices, flat sizes, etc. Our system is definitely faster than that of the Land Registry and it is open to the public for free," he said.

Free, but at what cost?

The Estate Agents Authority in June reprimanded Midland Realty (shops) - a subsidiary of Midland IC & C and a unit of Midland Holdings - fining it HK$10,000 for publishing false transaction information on its website.

A spokeswoman for Midland IC & C rejected suggestions that it published false information about certain transactions to boost sales or inflate transaction prices, but admitted "failure to verify the source of information after picking up it from newspapers".

In the first half of the year, the authority took disciplinary action against 199 agents for various breaches, ranging from providing misleading information to failing to conduct a land search for homebuyers. Of these agents, 100 received a reprimand, 33 were fined, 117 had new conditions attached to their licences and 22 had their licences suspended.

"In some cases, it is not easy for us to trace the source of information unless someone reports to the EAA," said Anthony Wong Wai-fung, the authority's director of operations, noting that the media does not disclose their source of information. "Before releasing information on property transactions to the public, estate agents should take steps to verify the accuracy of such information."

In August 2003, property agent Lai Chor-che at Centaline Property Agency's Sheung Shui branch was quoted in the firm's press release as saying a tourist from Shenzhen snapped up five flats at Choi Po Court, a Home Ownership Scheme housing estate in Sheung Shui, for a total of HK$2.64 million - in cash.

After receiving a complaint and on conducting a year-long investigation, the authority found out that the deal never happened. Lai's agency licence was suspended for two months in 2005 and Centaline was fined HK$200,000. Lai's licence was revoked last year as he was deemed unfit to hold a licence under the Estate Agents Ordinance.

Market observers say that setting aside the issue of accuracy, just the fact that so much information is concentrated in the hands of just a few key players is in itself disturbing. This, they say, allows those holding the gateway to property data to unduly influence the market outlook by talking it up. That, in turn, increases the risk of homebuyers splashing out more than they would under normal conditions.

Chan of Centaline, however, trains his sights on the media. The firm, said Chan, issues information on record-breaking transactions at the insistence of journalists. "The media is always keen to report big-ticket transactions, and we only respond to their demand. We also have information on flats that were sold cheap, but no one wants to write about those."