SCRAP metal thieves targeting valuable high-voltage electricity cables in Three Rivers are putting their lives at risk, police have warned.

Hertfordshire Police is investigating four thefts which have occurred in the past fortnight.

The most serious plunged thousands of Northwood homes into darkness on April 6, as reported in the Gazette last week, after a substation in Watford was broken into.

EDF Energy, which supplies gas and electricity in the area, was forced to cut power to carry out emergency repair work.

The company, together with police, has condemned the vandals responsible.

Amid fears that someone could be killed or suffer severe burns, police are appealing for information on three other incidents, including two in Moor Park.

A theft took place between March 6 and April 6, at a sub-station in Westbury Road, Moor Park.

Straps from an electricity transformer in a compound at Westbury Primary School, also in Westbury Road, were stolen between February 23 and April 6.

Thieves also took electrical cabling between March 24 and April 7, from Hampermill Pumping Station in Watford.

Chief Inspector for Three Rivers, Mike Marren, said: "Throughout 2009 and 2010, copper has increased in value, making it a much more attractive proposition for thieves.

"Patrols have been stepped up and we are working with the energy companies to prevent further incidents and catch the criminals involved, particularly because of the risks they run of severe burns and loss of their lives.

"Thousands of live high-voltage electricity cables run through these stations and they are out of bounds to the public for extremely good reasons.

"Only trained engineers should be entering these sites."

* Anyone with information or who has seen people acting suspiciously around a sub-station or loading or handling copper is being urged to call police on 0845 33 00 222.