Updated 12.46, adds Transport Malta fine.

A huge traffic jam that affected practically all of the south of Malta on Tuesday morning was caused by lax work by a contractor at the Santa Venera tunnels, a spokesman for Infrastructure Malta has said.

He explained that the contractor had cleared a water culvert in preparation for resurfacing works, and then simply covered it up with a steel plate. The plate shifted with morning traffic and the tunnel was reduced to a single lane.

A traffic jam quickly stretched to Marsa and then on to Tal-Barranni road, with motorists reporting being stuck for more than an hour.

In Qormi, a motorist said he was stuck in the narrow streets for 45 minutes as traffic was diverted from main roads.

One commuter said he left Żabbar at 7.30am - he only reached Blata l-Bajda at 9.15am.

The Infrastructure Malta spokesman said the agency had taken quick action to reopen both tunnel lanes, but it took time for traffic flow to be restored.

He said the incident was all the more regrettable because the agency had ensured that works were carried out at night, to minimise inconvenience. He said the agency has taken steps to launch legal action in terms of the contract.

Transport Malta has meanwhile, fined the contractor €15,000.