NEW DELHI (AP) — Two Indian navy sailors were missing and seven others hospitalized Wednesday after being overcome by smoke on board a diesel-powered submarine during a training exercise off Mumbai’s coast, an official said.

The incident is the latest for India’s navy, which has been plagued by accidents recently that have raised questions about its safety record.

The sailors were overcome by the smoke during a firefighting exercise, said Capt. D.K. Sharma, a navy spokesman.

A naval helicopter took seven of the sailors to a navy hospital in Mumbai, but two others were unaccounted for, he said.

The submarine did not suffer any damage and was heading back to the Mumbai dockyard, Sharma said, adding that an inquiry has been ordered into the incident.

Last August, another of the navy’s Russian-made diesel-powered submarines, the INS Sindhurakshak, caught fire after an explosion and sank at its home port in Mumbai, killing all 18 sailors on board.

The navy’s INS Talwar, a Russia-built stealth frigate, slammed into a trawler off India’s west coast this past December, sinking the boat and tossing 27 fishermen into the sea. All the fishermen were rescued.

Another navy frigate ran aground near the Mumbai naval base in January, causing damage to some equipment.