GUANGZHOU - Six people were being held for their roles in a power plant construction site accident in South China that killed nine workers on Saturday, according to the official investigation team.

The investigators, however, did not reveal more details about the people being held. The loss of balance was cited as the cause for the collapse of a 40-meter-high operation platform.

A local construction firm -- Dianbai Construction Group -- was responsible for setting up the platform.

The collapse occurred at around 8 a.m. at the construction site of No. 7 Thermal Power Plant in the district of Conghua, Guangzhou city, Guangdong province. Ten people were working on the platform when it gave away. Another worker below it was buried underneath the falling platform.

The two injured, being treated at hospital, are in a stable condition, hospital sources said.

The power plant is expected to start operations in May.