Seven hundred people have been evacuated from a block of flats in freezing temperatures following a “significant” gas leak.
Emergency services descended on Milton Mount Avenue in Crawley, West Sussex, following reports around 12.21am, with a major incident then declared.
Engineers later said a broken pipe was to blame for the chaos.
Experts say they hope people will be able to return to their homes later today.
Impacted residents have been placed in temporary accommodation until the scene is declared safe, while no injuries have been reported, according to Sussex Police.
Weather charts show temperatures plummeted as low as -11C in parts of the UK overnight, with more snow forecast to fall.
Detective Chief Superintendent Steve Rayland said the issue may take several hours to resolve, before urging everyone to stay well clear of the area.
Workers from gas company SGN said the cause of the leak was a pipe that had now been repaired.
Dan Brown, a spokesman for the firm, said: “We were called to assist emergency services overnight at a block of flats in Milton Mount Avenue, Crawley, following reports of a smell of gas near the building.
“Our engineers carried out several checks to our network and the surrounding area.
“We evacuated residents from 120 flats as a safety precaution and supported the local council in their efforts to arrange temporary accommodation in local hotels for those affected.
“We’ve been able to identify the source of the leak located at the rear of the property. Our engineers have since completed the required repairs to that gas pipe.
“We remain on site this morning carrying out further safety checks and monitoring gas level readings inside the building.”
Tina Belben, ward councillor for Crawley Borough Council, said: “The residents are tired and a little bit shocked but all very relieved that they are OK.
“They are in hotels in Crawley and the leak has now been fixed but the professionals want to make sure the building is safe to occupy before they let people back in.
“They did try to get everybody out as quickly as possible but they could not do what we would usually do and open up a leisure centre to put everyone in because of the coronavirus so there was a slight delay in getting everyone out, but they did a wonderful job.”
Resident Leah Hicklin said she was evacuated at 1.30am but said that others were still being led from the building at 4am.
She told the BBC: “We thought it was only something minor until they started evacuating the minor floors and then I was the top floor and I could smell gas.
“So they slowly but surely evacuated every single one of us.
“Some are in hotels, some are at family, some people really didn’t know where they were going. They’ve left pets behind and whatnot.”