HYDERABAD, India — A suspected carbon monoxide gas leak on Thursday killed six workers at a steel mill in southern India, police said.

The gas was being used for reheating after repair work at the mill in Padipari, a town in Andhra Pradesh state, police officer Surendra Reddy said.

The leak first killed three workers, then three others who tried to help them. Rescuers accounted for all the other workers.

The Press Trust of India news agency said the mill is owned by Gerdau, a leading Brazilian steel producer.

It's located in Anantpur district, 360 kilometers (225 miles) south of Hyderabad, the state capital.