An investigation has started following a fire at a house in High Wycombe, Buckinghamshire, which was being used as a cannabis factory.
Police were notified of the fire in Hughenden Road on Friday night by the fire service.
Fire crews put the fire out and found the building was empty.
Many rooms in the house had been converted for the cultivation of cannabis and a police cordon was put in place around the building.
The fire is believed to have been caused by an electricity overload caused by unsafe use of lights and heaters to grow cannabis, the police said.
The fire service has stated that about 50% of the first floor of the house was damaged by fire and both floors were smoke logged.
No arrests have been made at this stage, but police are looking for the people involved in the cannabis factory operation.
Det Con Simon Reid, of Thames Valley Police, said: "House to house enquiries are being conducted as part of our investigation, however I would appeal to anyone with information to come forward.
"I am particularly keen to hear from anyone who may have seen individuals either entering or leaving the house over the past few days and weeks.
He added: "Cannabis factories are illegal and not only do they fuel crime but also pose a serious hazard in terms of personal safety.
"They cause serious damage to properties when they are set up and draw more electricity than most homes.
"As a result, they can be extremely unstable and present a potential fire hazard, as was clearly the case last night."