Three foreign workers trapped inside a collapsed train tunnel have died despite rescue efforts that lasted over five days, Thai authorities have said, writes BBC.

The men, two from China and one from Myanmar, were still thought to be alive as recently as Thursday. They were trapped when part of the tunnel they were building collapsed on Saturday in Pak Chong district, about 200km north-east of the capital Bangkok. On Friday, authorities announced all three had died, with initial investigations suggesting this was due to a lack of air.

The tunnel, which was under construction and is part of the Thailand-China high-speed railway project, had collapsed due to a landslide at around 23:40 local time (16:40 GMT) last Saturday. Rescuers, comprising officials from the State Railway of Thailand (SRT) and a Chinese disaster response team, had been working round-the-clock over the past week with the hope of rescuing the victims.

They had tried to pump oxygen into the tunnel to keep the workers alive, but it is unclear whether the tubes they used reached the workers at all.

On Thursday, rescuers found the body of a Burmese truck driver buried under a pile of soil and rocks. The bodies of the two Chinese workers, a supervisor and an excavator operator, were found at about 06:00 local time on Friday.

All three bodies were found about 25 metres from the point of the tunnel collapse, officials had said.