KUNMING - Six people have been confirmed dead and nine others injured in a building collapse in Southwest China's Yunnan province on Monday, local authorities said on Tuesday.

Search and rescue work ended Tuesday morning after rescuers located all the 15 construction workers trapped in the debris, according to a press release from the Dali city committee of the Communist Party of China.

It said five of the survivors were in critical conditions and the other four suffered slight injuries.

The building, a steel structure in Xiaoguanyi village of Xiaguan township in Dali, toppled at 1:38 pm on Monday.

The local government sent more than 2,500 people to join the rescue work, which lasted for more than 10 hours, according to the document.

The collapsed building was an illegal structure built without a construction permit, and local authorities had asked its builders to suspend construction on March 15, said Zhao Hui, the city's publicity chief.

He said police had detained six people in connection with the accident. Investigation is under way.