Rescuers work in a collapsed railway tunnel in Funing, Southwest China's Yunnan province, July 15, 2014. Rescuers were working all out Monday night hoping to reach the 15 workers who had been trapped in the debris of the collapsed railway tunnel in Funing County. The tunnel, known as Funing No 1 tunnel, was on a 710-km railway linking Kunming with Nanning, capital of the neighboring Guangxi Zhuang autonomous region. Part of the tunnel, which was still under construction, collapsed at 4 pm on Monday. [Photo/Xinhua]

KUNMING -- Rescue work is continuing in Southwest China's Yunnan province after part of a railway tunnel collapsed on Monday afternoon, local authorities said.

As of 5:10 am on Tuesday, rescuers had managed to drill a hole in the collapsed tunnel and detected some responses, said Li Zhanguo, an official in charge of the tunnel construction.

"We are still trying to make sure of the workers' situations," Li said.

The tunnel collapsed at around 4 pm on Monday in Funing County of Zhuang and Miao Autonomous Prefecture of Wenshan, trapping 15 workers, according to the local government.

The tunnel, known as Funing No 1 tunnel, was on a pivotal railway linking Yunnan with southwest China's Guangxi Zhuang Autonomous Region.

The cause of the accident is still under investigation.