AUGUSTA — Maine authorities are warning residents of a chimney-sweeping scam being run by an out-of-state company not licensed to do business in Maine.

The attorney general’s office says a chimney-sweeping company named Aero Ventilation contacts homeowners either via phone or by knocking on their door, and offers a low-cost chimney cleaning.

But after taking a look, the Delaware-based company then says the home needs a new expensive chimney lining costing more than $1,000.

The operation appears to be happening in southern Maine.

Authorities remind homeowners to get a written contract before allowing a contractor do work on their home, and say residents have a three-day window in which to cancel the contract.

Suspicious contractors should be reported to police.