Warning of major commuter delays on M8 motorway in Sydney’s south-west

Sydney motorists are being warned of extensive delays this morning after water in a tunnel closed several lanes on the M8 motorway in the city's major thoroughfare through the south-west.

One lane in the tunnel between St Peters and Beverly Hills has just opened in both directions after being closed earlier due to late running maintenance overnight.

The closure was caused by fire sprinkler testing spilling too much water onto the road.

There are major delays on the M8 motorway in south-east Sydney. (Nine)

Motorway crews remain on site.

Drivers should continue to follow their directions and allow extra travel time as traffic is still heavy on the approach.

This is a developing story ... More to come.