The contract, which was awarded to Leighton Contractors (Asia) in 2013, involved the creation of two new underground platforms below the existing Hung Hom station.

The government confirmed in August that a diaphragm wall on the upper platform had been shortened and the number of metal couplers installed was 2,000 fewer than planned.

Contractor in scandal involving HK$97.1 billion Sha Tin-Central rail link made unauthorised design changes, Hong Kong government tells inquiry

In a 34-page interim report released on Wednesday, experts said there was “inevitable concern” that shoddy work also affected the lower platform, which would serve the cross-harbour section of the rail link connecting Hung Hom to Admiralty.

The upper platform would serve the New Territories to Kowloon section of the link.

“Other irregularities have been reported or discovered. They include the inconsistencies in records provided by the MTR Corp; honeycombs [hollow spaces in concrete which could reduce structural strength] and voids in the soffit of the [upper] platform slab; and possible issues in the construction of the diaphragm walls,” the report read.

The government earlier said “huge discrepancies” had been found in drawings the MTR Corp submitted in June and July, prompting a police investigation.

Experts suggested the MTR Corp review its records to check whether other irregularities might be found, but said the railway firm had not yet provided any information.

While the MTR Corp had arranged to test the structural strength of the upper platform with a loading test, experts wrote in the report that this would be insufficient.

“The [team of experts] is not convinced the load test can address the structural safety, long-term durability and serviceability of the built structures,” they wrote.

Following discussions, the MTR Corp agreed to put together a test proposal, which involved breaking open parts of the platforms and “non-destructive tests”.

The report also stated the railway firm had submitted a proposal on October 15, which was rejected for having limited scope.

The MTR Corp suggested breaking open 10 spots on the upper platform and none on the lower platform, or the diaphragm wall.

“The government has requested the MTR Corp submit a strategy conforming to the recommendations of the [experts] by the end of this month,” a government spokesman said.

The report, however, read that the railway firm asked to delay the submission deadline to mid-November.

The trio of experts and former senior officials – Lau Ching-kwong, Hui Siu-wai and Wong Hok-ning – will submit a final report in May 2019.

Whistle-blower in MTR scandal involving HK$97.1 billion Sha Tin-Central rail link blasted by contractor at inquiry

Civic Party lawmaker Tanya Chan said the experts appeared to be dissatisfied with the MTR Corp’s responses.

“The report’s tone is harsh; it slams the MTR Corp for submitting late and useless information,” Chan said.

She insisted the Legislative Council needed to launch a separate investigation under the Powers and Privileges Ordinance, which would give lawmakers the ability to summon witnesses and request documents from relevant parties.

Veteran engineer Ngai Hok-yan said ultrasound scans could be used for non-destructive tests on the platforms and the process may take only days to complete.

After that, test conductors may locate suspicious areas to break open.

Ngai believed this process could take up to two months, depending on manpower.

The engineer added a loading test at this point may have limited use.

“If you break up the concrete and find problematic works … the loading test won’t put people’s mind at ease,” Ngai said.

He warned it could take a long time to locate all the affected spots if the conductors found honeycombs during the test.

It would also take a long time to repair them, he said.