About 100 mainland and Hong Kong officials attended the event, which was not publicised in advance, and the news media were not invited.

MTR Corp seeking more flexible baggage rules for high-speed rail link

The chief executive described the event as “a little working level handover procedure”.

She also responded to new concerns over the long-delayed and overbudget rail link.

On reports of a “secret floor” at level B5 of the terminus providing a short cut to the rail platforms, Lam said the basement area was similar to a hotel’s “back of house area” and was not something “mysterious”.

“If you’ve stayed at hotels before, you would know hotels have [facilities] called ‘back of house’, where maintenance is carried out,” she said.

On the issue of mainland officers manning the joint checkpoint, which will open between 6.30am and 11.30pm daily, Lam said they would not remain in Hong Kong after they finished their work for the day, though some would need to do overnight shifts in the run-up to the rail link’s opening. The government had stated last year that these personnel would not stay overnight.

Meals would be provided for them as they were not allowed to leave the port area for food, but mainland authorities would pick up the tab, she said.

“The cost of all these meals as well as the cost of all the other expenses, like cleansing, collecting rubbish, electricity and water, are all picked up by the mainland authorities, but we need to help them to arrange these things. It’s as simple as that.”

With the rail link opening in little more than two weeks, Lam said she had told government bureaus and the rail operator to quickly address any public doubts or concerns.

“Apparently and unfortunately, anything related to the high-speed train is normally presented with some worries and anxieties,” she said. “I don’t want this to continue to repeat itself.”

The Transport and Housing Bureau later said the 3,100 square metre basement had been mentioned in a document submitted to the Legislative Council in 2016. It would be used for rescue and evacuation purposes, the bureau said, and only those with a permit issued by the MTR Corp would be able to access it.

On the number of officers remaining overnight at the terminus, a Security Bureau spokesman said it was up to mainland authorities to reveal relevant details.

“Information related to mainland personnel stationed [at the terminus] is considered mainland affairs,” the spokesman said.

Priscilla Leung Mei-fun, of the pro-establishment Business and Professionals Alliance for Hong Kong, agreed that officials needed to be more transparent about all matters concerning the cross-border rail.

“There is a crisis of trust [between people and the government],” Leung said. “It’s best that the MTR Corp and the government make everything public … This can reduce many questions.”

The Hong Kong Journalists Association said the government had “seriously undermined the people’s right to know” with Monday’s “inappropriate” arrangement.

“We question the government on whether they have deliberately held the ceremony in a low-key manner,” it said in a statement.

Because of the high level of public concern over the express rail, the association said, the media should have been invited to cover the handover event and interview officials involved.

Separately, mainland media quoted a staff member of the West Kowloon terminus as saying train ticket sales would start on September 10.

The MTR Corp did not confirm the date but said it would announce details later this week.