Metal thieves are “risking life and limb” to make money, after workmen discovered crooks had targeted an electricity substation.

A 1m by 70mm length of copper earthing wire was ripped from the unmanned building in Billet Lane, Hornchurch.

Workers from UK Power Networks, which owns the site, made the discovery on Saturday afternoon.

A Havering Police spokesman said: “These people are risking life and limb for a very small profit. There is a very real chance of getting electrocuted if you mess about in an electricity substation.”

He added it was likely the thief had a “working knowledge” of the building or similar buildings.

The theft did not affect power supplies.

Sustations carry ‘Danger of death’ signs to warn the public of the possiblity of electrocution.

A spokesman for the UK Power Networks said: “This substation converts our 11,000 volt high voltage network to our 415/240 volt low voltage network.

“UK Power Networks is committed to providing a safe, reliable electricity service. Anyone who tampers with our electrical equipment is risking their lives and those of others who could come into contact with damaged equipment and such crimes can cause widespread power interuptions.

“We are constantly working to stamp out such incidents, particularly because the risks involved are horrendous, including severe burns and the loss of life in some cases.

“This matter was reported to the police and we will always assist them with their investigations and support prosecutions, which can result in large fines or even prison sentences. Anyone who notices anything unusual or suspicious in or around the substations providing their home or business with power is urged to contact the police and phone us on: 0800 587 3243.”

Anyone with information should contact Romford police station on: 0300 123 12 12.