Lawmakers stepped up pressure on the MTR Corporation and the government to come clean about the two-year delay to the high-speed rail link, even threatening to invoke the legislature's special powers to investigate it.
They say many questions remain unanswered on the postponement of the HK$67 billion line to Guangzhou.
The issues include whether the MTR could really blame damage to a tunnel-boring machine, given that reports of delays emerged before the heavy rains blamed for the damage.
The MTR also cited unexpected complications relating to the geology of the West Kowloon terminus site.
The Labour Party's Lee Cheuk-yan said transport minister Professor Anthony Cheung Bing-leung's claim to have been "totally caught by surprise" showed that the government was not keeping a close enough watch on the project.
"I don't understand why the government has done such a bad job in monitoring the construction," he said.
Lee urged the Legislative Council to invoke its Powers and Privileges Ordinance to launch an investigation if the MTR and government fail to offer satisfactory answers. He also suggested Legco hire a consultant to study MTR and government documents.
Lawmakers Wu Chi-wai, of the Democratic Party, and Gary Fan Kwok-wai, of the NeoDemocrats, also suggested invoking Legco's powers under the ordinance, which would allow it to summon officials to give evidence and order the release of government documents. Engineering sector lawmaker Lo Wai-kwok said the MTR should have done more to explain the delay after it was criticised for giving just a 30-minute press conference on the announcement.
"It's a big issue, so more time was needed for better explanation," he said.
Lo said a Legco investigation could take a long time and he would rather see the MTR and government devote more time to tackling the construction delays.
The rail link, which will connect Hong Kong to the mainland's high-speed network, attracted huge controversy even before the delay was announced.
For its distance, it is the world's most expensive railway. The loss of Tsoi Yuen Tsuen village in Yuen Long to make way for it prompted protests in 2011.