Rescue teams dispatched sniffer dogs to search for survivors trapped in a collapsed train tunnel in Thailand.

Officials deployed the K-9 unit to the underground railway project under construction in Nakhon Ratchasima province on August 26.

Backhoes were also at the scene to clear the debris.

The tunnel, set to link Thailand to China, reportedly caved in and trapped workers despite no rain falling on August 24 evening.

Authorities said three people working in a section some four kilometres from the entrance were buried alive.

They were identified by officials as Chinese foreman, Hu Xiang Min, a Chinese backhoe operator, Dong Xin Lin, and a Myanmar truck driver.

Rescue teams said they detected signs of life through the earth and inserted a 'rescue tube' with a 1.2-metre diametre hoping the three men could be evacuated through it.

The rescue tube will also supply air and emergency supplies until the workers can be reached.

The Hunan Sunshine rescue team from China has also arrived in Thailand to join the search and rescue.

The Thai government is building a high-speed railway connecting Bangkok to Kunming, China. The project was expected to be completed in 2028.