New Delhi  - Six labourers were killed when poisonous gas leaked at a ceramic plant in Morbi town in India's Gujarat state, reports said Saturday.

The labourers were cleaning an underground tank at the Comet Ceramic Company at Morbi, about 260 kilometeres west of Gujarat capital Gandhinagar, when they lost consciousness after inhaling the poisonous gas, PTI news agency reported.

They were taken to a local hospital where the doctors declared them dead, the police said.

Police have registered a case of accidental death and is investigating the cause of the leak.

Workers routinely clean sewers and underground tanks in India without protective equipment or clothing leading to similar accidents. (dpa)