A fire that broke out in the Srisailam hydroelectric plant on Thursday night has left nine persons dead, most of them engineers, with thick smoke hampering rescue operations for over 12 hours.

Three people were badly injured in the blaze at the plant on the Telangana-Andhra Pradesh border.

Telangana energy minister G. Jagadish Reddy said the fire broke out late on Thursday night when 17 people were inside the plant, run by the Telangana State Power Generation Corporation. Eight employees managed to come out, he said. Thick smoke engulfing the area hampered immediate rescue operations, the minister said.

“A total of 17 employees were at the plant at the time of the accident. Eight of them were able to come out. But the remaining nine (seven Genco employees and two private firm employees) who were trapped were tragically killed. They tried to save the plant till their last breath,” Reddy told reporters at the plant.

A fire department official based on preliminary assessment said the blaze started in the battery area apparently due to “over voltage”, which needs to be established after a thorough investigation.

Telangana chief minister K. Chandrashekar Rao ordered a CID inquiry.