Police are investigating the source of a document purporting to be an official press release saying that the government would announce new measures to rein in the property market.
The Secretariat Press Office referred the matter to police in a bid to ease fears among internet users after the document was widely circulated last week.
The force said that the commercial crime bureau was investigating.
Anyone who accesses a computer with criminal or dishonest intent is liable to a jail term of up to five years under the Crimes Ordinance.
Internet users had speculated that a press conference was to be jointly held yesterday by Financial Secretary John Tsang Chun-wah and the Monetary Authority to announce the new measures.
Rumours have been swirling since last week on online forum Discuss Hong Kong and through messaging tool WhatsApp.
Some suggested that the buyer stamp duty - introduced in October at a rate of 15 per cent of the property price for non-local buyers - would be increased further, to 30 per cent.
Some cited "internal information" that the government planned to offer 10,000 long-term pre-sale contracts for flats under the Home Ownership Scheme in the first quarter.
There was also speculation about a ban on mortgages for anyone who already owned two homes.
The "new policies" were in a document that mimicked the wording of a genuine press release issued last year, which detailed the government's measures to curb the property market. The only information changed was the dates and tax rates.
"A press release circulating on the internet saying that the government would take further measures to address the overheated property market is fraudulent," stated an official press release.
"[The government] strongly condemns those involved in forging the press release for spreading a malicious message to disrupt market order."
Acting Chief Executive Carrie Lam Cheng Yuet-ngor said: "The public must be very careful now, because the property market is heated."
The Estate Agents Authority said dealers issuing misleading or fake market information could face disciplinary action.