THREE police forces are now investigating potentially lethal letter bombs sent to four addresses in the North of England, all of which are connected with agriculture.

Two bombs have been sent to addresses in North Yorkshire, with the most recent victim being a 58-year-old sheep farmer from Ripon, who opened a parcel bomb containing carpet tacks last Friday.

He escaped with cuts to his face, but the blast was powerful enough to destroy a chair and other furniture.

The farmer, who has not been identified, because police fear he could be targeted again, was taken to hospital for treatment and later allowed home.

The first bomb to be received in North Yorkshire, arrived on December 15 at Ritchey Tagg in Masham, which makes ear tags for sheep and cattle.

Luckily, a receptionist escaped unhurt after opening the package, but only because she opened it at the wrong end.

A woman opening mail at Frank Hill and Sons estate agents in Patrington, East Yorkshire, was not so fortunate.

The firm deals with livestock auctions, and a similar letter bomb containing nails was sent to them and it exploded in her face, resulting in eye injuries which required hospital treatment.

A six-year-old in Congleton, Cheshire was the youngest victim. She needed hospital treatment after a letter-bomb sent to her home address peppered her legs and feet with pins and small ball-bearings.

The address is also used for a pest control business.

All four bombs were sent in Jiffy bags, and officers believe the incidents are linked.

The officer in charge of the investigation, North Yorkshire deputy chief constable Peter Walker, is working closely with officers from Cheshire Constabulary and Humberside police.

He told a press conference last Friday the attacks could have been carried out by an animal rights fanatic, a theory backed-up by Animal Liberation Front spokesman Mr Robin Webb.

Mr Webb said he would not be surprised if an extremist splinter group was behind the bombs and that there are two organisations which would see the victims as casualties of a struggle.

The Justice Department, formed in 1993 and the Animal Rights Militia, formed in 1984, both have said they were prepared to harm those responsible for harming animals, but neither has claimed responsibility for these bombings.

As a result of the letter-bombs, agricultural firms are being urged by police to mark any packages they send clearly, and if they receive any post which is suspicious, they should leave it unopened and dial 999.

Mr Walker said: "None of the victims have been people engaged with animal experiments, they are merely members of the farming community going about their business.