Hundreds of engineers are visiting homes in the Falkirk area as part of a major operation to tackle a gas network failure.
Thousands of people spent the night without heat in freezing temperatures after the outage on Sunday morning.
Heaters and portable cookers have been distributed to vulnerable residents and 14 schools and nurseries are closed.
Gas infrastructure company SGN said it had now begun reconnecting supplies to homes across the area.
The company said previously that it had hoped to visit all 8,000 affected properties by Monday afternoon.
By 21:30 on Monday, SGN confirmed it had reconnected gas to 3,000 properties.
More than 250 engineers are going door-to-door to turn off gas supplies at the meter for safety reasons.
Falkirk Council said the majority of schools in the area, as well as Kinnaird Waters early learning and childcare centre, would reopen on Tuesday.
Bainsford primary school and nursery class, Larbert early learning and childcare centre, and Kinnaird primary school and Thistle Wing will remain closed.
SGN has warned some homes could be without gas supplies until the weekend in the “worst-case scenario”.
Mother-of-four Angelene Perry, who has a nine-month-old baby, said she had borrowed four radiators from a friend and has been given a stove and two fan heaters by SGN to heat one room.
She said: “We’re using the kettle just now to boil all our water.
“I’m just thinking at the moment how I’m going to go through the week, and just really thinking about night time.
“During the day we’re OK, we can huddle into one room, but just trying to plan ahead for the week.”
SGN spokesman Denis Kerby said they were working to restore supplies as quickly as possible.
“That might be a couple of days but in terms of getting everyone back on, we’re looking at five days,” he told the BBC’s Good Morning Scotland programme.
“It could be up to Friday, it could even creep into the weekend – that is really the worst-case scenario.”
He said engineers needed to visit every home even if residents have managed the turn off their own supplies.
Mr Kerby said that SGN apologised for the fault as it was “our piece of equipment that’s failed.”
He said: “However, what we are doing is making sure people are getting their gas back as quickly as possible.
“So this is making sure that no one who has a vulnerability is going to be missed.”