A burst water main next to Shepherd’s Bush Green caused chaos on Thursday when it flooded the surrounding roads.
The incident happened on the eastbound carriage of Uxbridge Road at around lunchtime.
Around 500 Thames Water customers have reportedly lost their water and there is also traffic congestion.
Police said Uxbridge Road westbound is closed and just two of three lanes are operating on Shepherd’s Bush Green.
The National Grid has been carrying work gas mains replacement work in Uxbridge Road.
A spokesperson said: “At around midday today our engineers were digging down to locate one of our gas mains in Uxbridge Road near the junction with Hopgood Street when water began to enter the excavation.
"We immediately alerted Thames Water and the local authority.
“We will do what we can to help resolve the incident as soon as possible.
“It’s too early to say what caused the water ingress into our excavation and we will do all we can to assist with any investigation.”
A Thames Water spokesperson said: “We’ve now stopped the flow of water from our 24-inch pipe, which was damaged during work by a third party, and are ready to start repairing it.
“In the meantime we have a team dedicated to re-routing water around our network of pipes to get customer supplies back to normal as quickly as possible. We expect this to take until later on this evening.”
The spokesperson added the work being done by National Grid is in no way related to Thames Water.
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