BHUBANESWAR, India (Reuters) - At least nine Indian miners were killed and nearly two dozen trapped when mine waste collapsed at a coalfield run by state-owned Coal India Limited, officials said on Friday, hitting production at one of the country’s largest mines.

The accident occurred in Jharkhand state on Thursday evening at the Lalmatia mine owned by Eastern Coalfields Limited (ECL), a subsidiary of the world’s largest miner.

“So far, nine bodies have been recovered,” R.R. Amitabh, a general manager at the ECL project office told Reuters. A rescue operation was underway and the exact number of people trapped had yet to ascertained, he said.

Coal India has a poor safety record, with 135 accidents reported last year, killing 37 people and injuring 141, the company said in a report, highlighting concern about working conditions.

Operations at the mine in Godda district, about 280 km (175 miles) from the state capital, Ranchi, have been stopped, Amitabh said.

The mine has an annual capacity of 17 million tonnes and accounts for about half of ECL’s coal production, he said. Last month, ECL accounted for about 9 percent of Coal India’s total production of 50 million tonnes.

Mine waste piled up near the mine caved in, state police spokesman R.K. Mullick said.

“At that time, about 40 people were working in the mine and some of them managed to escape. Some of them have injuries,” Mullick said.

The operation of the mine had been outsourced to a private company, Mullick said.

The federal Coal Ministry has ordered an investigation.

With coal accounting for about 70 percent of India’s power generation, the country is the world’s third-biggest producer and importer of the fuel, and government wants to boost domestic output to cut imports.

Coal India, however, has failed to meet its output targets for years due to several reasons including strikes, accidents and protests.