Officers say burglars entered the upstairs accommodation on Ribbleton Lane and set fire to a wardrobe. Luckily the occupant was not at home.
It is believed the incident occurred sometime between midnight and 1.30am on Saturday. The offenders are suspected to have stolen property before making off.
Police were called to the scene by fire crews from Preston and Penwortham who tackled the blaze and restricted it to the lounge area of the flat above a shop. Initially it was believed there were people still inside.
Officers are now keen to speak to anyone who witnessed the incident or who may have information that could lead them to the offenders.
DS Oliver Jemson, of Preston Police, said: “Luckily the occupant of the flat was not home at the time of the incident, or this could have been much more serious.
“When officers arrived at the scene there were several people in the area and we believe somebody may have seen something that could help us with our enquiries.
“If you know anything about the incident, please get in touch.”
Anyone with information should contact police on 101, quoting log number 105 of April 23.