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."
Why does an engineer have to visit homes?
Residents have been told they could be waiting for up to five days for their supplies to be restored.
To ensure the gas supply is managed in a safe way:
- Customers are initially told by the gas emergency service to turn off the gas themselves at a switch beside their meters
- Engineers have to check every home to ensure the gas has been turned off before it can restore supplies
- If the gas is not fully off, when the supply is restored it could quickly fill the home
- Some homes that receive gas from other parts of the network will still have supplies
- Once the gas is back in the network, engineers make return visits to homes to reconnect supplies
- Engineers need to relight some boilers and check that appliances are working safely
If gas meters are inside homes, engineers must be given access, however, if they are outside (in a white or brown meter box) access is not needed.
Affected householders will be compensated for their time without gas. Find out more here.
A problem with a "governor" station which regulates gas pressure in the local network developed at about 04:30 Sunday.
Thousands of people woke up to discover they had no heating or hot water as their boilers shut down.
SGN said homes in Bainsford, Carron, Carronshore, Larbert, Langlees, New Carron Village, Skinflats and Stenhousemuir were affected.
Meanwhile, residents have also been warned to be "mindful" of their electricity use, following a number of power outages in the area overnight.
On Twitter, police said: "Scottish Power is asking people in the Falkirk area is to be mindful of their electricity use over the coming days as there's increased demand on the electricity network with people using heaters while they're without gas.
With overnight temperatures dipping below zero, people living in the area are being urged to check on vulnerable neighbours.
Falkirk Council made the Camelon Community Centre available to SGN, which was handing out portable heating and cooking equipment to elderly, sick or disabled customers and those with young children.
A mobile catering unit was also distributing hot food.
Mr Kerby added: "Our priority is vulnerable customers. We are liaising with the local authority and our partners in the community to make sure we can visit all the people who may need that extra bit of help.
"We would also appeal to people to be really good neighbours - and please check on any elderly neighbours or anyone in the vicinity who may need some extra help."
One local resident, David McCallan, told BBC Scotland that his home was like an "ice box" when he woke up on Monday morning, until he switched on a heater supplied by SGN.
"It's not a great heat but it's sufficient to keep myself and my wife warm enough."
Customers can request heating or cooking appliances by calling into Camelon Community Centre.