HANGZHOU, Jan. 28 -- Seven workers were killed when an Indian oil tanker exploded and caught fire at a shipyard in east China's Zhejiang Province on Tuesday morning.

Smoke was detected followed by the explosion around 7:20 a.m., when the seven workers were repairing the tanker at the Haizhou Shipyard in Daishan County in the city of Zhoushan, said a spokesman with the provincial work safety supervision bureau.

The oil tanker, which has an oil load capacity of 50,000 tonnes, was unloaded when the accident happened.

All the victims were Chinese, said the spokesman.

The cause of the accident is under investigation.