Officers are appealing for witnesses after two fires, thought to be suspicious, took place on a single night in The Grange estate, Daventry.
Police and fire were called to a house fire in The Stour at 4.45am on Monday, February 18, which centred on the front porch area.
Two adults and three young children reached safety by escaping via the back of the house.
Shortly after 5am, also on Monday, February 18, a fire to a car in the nearby street, Dee Walk, was reported to Northamptonshire Fire and Rescue Service.
This fire also spread to two further cars.
Daventry sector Sergeant Chris Thomas said: “Both crimes are being treated as suspicious and being jointly investigated by the police and fire service.
“We would urge any witnesses or anyone who has information about these fires to please report this to the police or Crimestoppers.”
Work is on-going in Daventry as part of Operation Unite, which is tackling levels of arson and anti-social behaviour in the area.
Anyone with information about these fires should contact Northamptonshire Police on 101 or make an anonymous report to Crimestoppers on 0800 555111.
Arson prevention advice:
Avoid placing bins, rubbish, or other combustible items against the walls of your home. These are a ready supply of fuel for an arsonist.
If rubbish can only be stored alongside your building, then please avoid putting it directly against the wall of your home, to minimise the chance of fire spreading.
Do not allow rubbish to accumulate in areas outside your home. Piles of discarded waste can be targets for deliberate fire setters.
Ensure you only place rubbish out for collection on the correct day.
Maintain good security in and around your home. Remember to close and lock any gates. Lock doors and windows when you go out. Make sure fencing is in a good state of repair.
Consider installing security lighting at your home to deter intruders.
Sheds and garages should be locked. Do not leave flammable liquids in the open.
If you see fly-tipped waste, then please report this immediately. Fly-tipped rubbish in the Daventry area can be reported by visiting www.daventrydc.gov.uk/online or by calling Daventry District Council on 01327 871100.