Residents had to be evacuated from their homes after a burst pipe flooded a north London street.
Twelve fire engines and around 80 firefighters were called to assist with the incident in Queens Drive, Finsbury Park.
Video footage posted online on Tuesday morning showed roads submerged in ankle-deep water.
A London Fire Brigade spokesman said the flooding had affected a 500 square metre area and that people were being evacuated from their properties.
Thames Water said one of its large water mains had burst and that specialist engineers had been called to the scene to stop the flow.
A spokesman for the company said that, due to the “complexity of the work”, it could take until midday to resolve the issue.
London Fire Brigade said crews were called to the scene at the junction of Queens Drive and Princess Crescent at 7.47am.
Abi Glover, 27, who lives in a first-floor flat at St John’s Court in Queens Drive, told the PA news agency that the ground-floor properties in her building were “completely flooded”.
She said: “The water started at 7.40am and it has not stopped. Everyone has been wading out with no shoes on.
“The police had a go at me for leaving, but I am in a flooded building.
“It’s like a river out there, I think that’s why police had a go at me – because the current is so strong.”
Hackney London Borough Council said it will be opening a rest centre for residents whose homes have been affected.
The council added that Parkwood Primary School in Queens Drive has been closed as it does not have running water.
Matthew Christian, who lives next to Manor House Underground station, told PA: “It’s really shocking to see that amount of water flooding the streets with such power that it’s ripping up the road and rushing down the street into people’s front gardens.
“It’s not the kind of thing you expect to see in Finsbury Park on a Tuesday morning in October.
“The water is ankle-deep in some parts. I saw some people coming out of their homes where the water was going in and wading up towards us.”
Karim Traboulsi, who also lives in Queens Drive, told PA that he was woken up by the noise of the water.
He said: “My first thought was ‘I probably won’t be able to make it to work’.
“Now we’re a bit worried about our elderly neighbour in the basement flat.
Footage taken of Queens Drive showed fast-moving water flowing down the street, with cars still parked on the road.
A Thames Water spokesman said: “We’re sorry to any customers affected by our burst main this morning. We’ve sent our specialist engineers to the scene as a top priority, and they will be working hard to get everything back to normal as soon as possible.”
The company said the burst main was causing the following areas to experience low water pressure or a loss of supply: Highbury, Highbury Fields, Canonbury, Kings Cross, Islington, Pentonville, De Beauvoir Town, Hoxton, Camden, Holloway, and parts of Barnsbury and Tufnell Park.