A railway tunnel has collapsed and trapped six workers in southwest China's Yunnan Province, and more than 200 rescuers are still struggling to save them, local authorities said on Thursday.

Rescue workers walk past a collspsed tunnel in in southwest China's Yunnan Province. Six workers were trapped. [Xinhua]

The six people were working underground when the collapse occurred at about 11:00 p.m. on Tuesday night in a railway tunnel at the Songgui Township of Heqing County, said Zhang Donghua, an official with the railway authorities of Kunming, capital of Yunnan Province.

The six people were contacted by rescuers via a phone line at about 4 a.m. on Wednesday, and they said they were safe. But they later lost contact due to a further collapse, Zhang said.

By Wednesday midnight, rescuers had succeeded in using a pipeline to send oxygen and food to the six people.

The railway tunnel is being built to link Dali and Lijiang, twoscenic spot cities in Yunnan, and the section where the collapse occurred has a length of 1,268 meters.