About 90 workers were injured Monday when an oil rig being built at a shipyard in Singapore tilted to one side, the Ministry of Manpower said, amid reports of explosions and snapping cables.

One worker was in critical condition and 22 others were seriously injured during the incident at the Jurong Shipyard, the ministry said in a statement.

"Preliminary findings indicate that the jack-up mechanism of one of the legs of a three-legged jack-up rig had failed, causing the rig to tilt to one side," the ministry said.

"Some 90 workers have been sent to four hospitals -- the majority had minor injuries with one worker in a critical condition and 22 seriously injured."

It said that all work activities on the rig, being built at the shipyard, had stopped. Local media reports quoted workers as saying they heard loud explosions and saw cables snapping as the oil rig tilted.

Jurong Shipyard Pte Ltd is a wholly owned subsidiary of Sembcorp Marine Ltd, one of two major oil rig makers in Singapore, the other one being Keppel Corp.