AN investigation is underway after four cars were damaged in a 'suspicious' fire at an industrial estate.

The incident happened at Rosewood Industrial Estate in Blackburn at around 4.45am.

Firefighters said two cars were on fire and two others were damaged by heat.

A fire service spokesman said: "The cause of the fire is unknown at the moment.

"The fire is being treated as suspicious.

"We're investigating with the police to find out how it started."

Nobody was injured in the incident.