Gardai suspect a fire in Buncrana overnight may have been started maliciously.
An oil tank caught fire just before 4am in the centre of the town.
The oil tank, which is caged, caught fire but was brought under control by members of the fire service.
The tank belongs to a building which belongs to the HSE and is surrounded by a number of other businesses and private residences.
An investigation has been launched into the cause of the fire but one of the theories is that the blaze was started maliciously.
Nobody was injured in the blaze.