A barge had sunk in Ha Long Bay at the time a cruise ship decided to bypass the popular tourist spot, the Travel Industry Council, which is investigating the incident, has been told.
But it is still unclear whether this was the reason the Costa Victoria skipped the Unesco World Heritage site.
Council chairman Michael Wu Siu-ieng said he had received verbal confirmation from the Vietnamese consulate in Hong Kong that the vessel had sunk, and a written reply with further details, such as when and where the boat sank, was expected in a few days.
Some 300 passengers, including pro-establishment lawmaker Ann Chiang Lai-wan, staged a sit-in on the Costa Victoria on February 6 in protest against Miramar Travel's offer of HK$340 compensation for missing out on the tourist spot. The agency claimed a sunken barge in Ha Long Bay was the reason it skipped the site, but some passengers doubted the explanation.
They later reached a compensation deal with the tour agency but did not disclose the amount.
Wu said yesterday he hoped the council's investigation report would conclude the incident.
"We hope to see whether the time and place the boat sank matches the cruise ship's story," he said. "But we are not the captain and we were not there. On whether it was safe to berth, the cruise company should make that decision. The important thing is whether or not the accident happened."
Some 2,000 passengers due to depart on the same cruise were forced to miss their stop at Hainan Island because departure was delayed by eight hours as a result of the protest.
Costa earlier said it reserved the right to sue the protesters. It said it was complying with instructions from the Vietnamese port authorities when it decided not to berth.