TWO police officers sniffed out a suspected cannabis factory - after noticing an unusual smell while chasing a burglar.

It resulted in the recovery of 300 plants and hydroponic equipment from a house which appeared to be derelict in Blackburn Road, Darwen.

The PCs were struck by the odour when they got out of their patrol car near the suspected cannabis factory.

They had been called out to help find a burglar, who was reported to have just struck, but left that to colleagues as they tried to discover where the smell was coming from.

Police said that at about the same time they had been alerted by neighbours about activity in the house.

As the PCs noticed the smell, residents had called the police to say they could hear noises from the property in Blackburn Road, which was boarded up and had the appearance of being derelict.

Officers from the support unit were despatched to the scene and raided the house, making four arrests.

It is not yet clear if anyone owned the house or if it was derelict.

Detective Sergeant Paul Ryan said: "The officers were in the area investigating another address and they smelt it.

"It was a terraced house and we believe all three floors where utilised for the growing of cannabis.

"We recovered 300 plants and they are currently undergoing tests. We also recovered a hydroponic system."

Three men have been charged with producing and being involved in the supply of cannabis.

They are due to appear before Blackburn Magistrates' Court later this week.