Firefighters turned crimefighters when they discovered a cannabis farm.

Some 50 plants were found by Wallington firefighters investigating a flood in a block of flats in New Road, in Hackbridge, last Thursday.

They were called to a flat after water started to gush through the ceiling at about 11pm.

When they broke in to the unoccupied upstairs to investigate the cause they found the flat was full of cannabis plants.

The watering system in the sophisticated growing setup had malfunctioned, flooding the flat.

Police have now launched an investigation in to who was growing the plants. It is understood none was living at the flat.

White Watch firefighter Michael Fagan said: "Its not the usual thing we find when we are called out to an incident, but its all part of the job."

He described the setup as "professional" with powerful lighting, fans and a watering system.

The 24-year-old resident of the downstairs flat that flooded, said: “The water was coming through like a shower.”

“I went and banged on the door to tell the person inside what was going on, but there was no answer, so I dialed 999.”

She said she had no idea about the cannabis farm, but she had become suspicious by late night “comings and goings” by “dodgy people” to the flat.

She said she had never smelt the plants.

She said: “I think they (the criminals) may have chosen here because we are in such a quiet place.”

The block of flats was in part of a new-build private housing estate at the end of a cul-de-sac.

A police spokesperson said: "If anyone has any information about the occupants of the flat or information about the cannabis factory then please contact Sutton Police Station on 0300 123 1212 quoting ref no: 4001036/11. Alternatively, contact Crimestoppers anonymously on 0800 555 111."