Police swooped on a suspected £500,000 cannabis factory during a dramatic dawn raid at a house in central Bradford.

Officers were alerted to the Grove Terrace property, Great Horton, by the crew of the West Yorkshire Police helicopter, who used specialist equipment and detected a suspicious amount of heat emitting from the building.

A police spokesman said four men jumped from a window at the house and ran off.

Police say 1,125 suspected cannabis plants, with an estimated street value of half a million pounds, were found in the cellar at the property.

The suspected factory was closed down in a combined operation involving the police helicopter, Bradford District Drugs Team and Bradford South Police.

Officers forced entry into the property early on Tuesday morning and found the plants.

PC Dave Jackson, of the Bradford District Drugs Team, said: “This is a significant seizure and one of the biggest we have seen in the area for some time.

“It doesn’t matter how big or small the farms are, however. If you have a suspicion that plants are being grown in your area, please contact us immediately and we will make the appropriate enquiries.”

Sergeant Matt Walker, of the City Ward Neighbourhood Policing Team, said: “We are having some real success in disrupting the drugs markets in Bradford but we need the public’s help to sustain our activity.

“Residential properties, both private and rented, are increasingly being used by individuals looking to make money from growing and selling cannabis.

“We would ask landlords to be vigilant. Dealers often rent to distance themselves from the property. They may also be reluctant to register utility bills in their own name and often run up high gas and electricity bills.”

John Redpath, whose coffee shop, Spud Murphys, is located on the corner of Grove Terrace, opposite the two raided terraces, believed the ownership of the properties had recently changed hands.

He said: “An elderly couple owned them for about 15 years. They’ve been occupied by students. I gather the doors were bolted from the inside.”

A ginnel runs behind the row of houses which are immediately next door to Bradford College’s library in Great Horton Road. The properties are just yards from the College’s main entrance.

A 23-year-old resident in Horton Grove, a recent Bradford University graduate who did not want to be named, said: “I have smelt cannabis in the street before but I’m surprised this has been going on so close to the university and my home.”

l Four males were arrested and appeared at Bradford Magistrates Court yesterday charged with the production of cannabis, between July 1 and August 4.

Canh Trong Bui, 30, of no fixed address, Trung Phan, 37, of no fixed address, and two teenage boys, who cannot be named because of their ages, were remanded back into custody by Bradford magistrates.

They will next appear at the court on August 11.