A flesh-eating bug in a batch of heroin has sparked a national alert as a woman fights for her life in hospital.

Health chiefs in Lancashire are contacting A&E departments across the country warning staff to look out for symptoms of the bug which has already killed two men in Preston.

Addict Gary Preston, 35, died in the Royal Preston Hospital on Sunday after injecting heroin.

Tests revealed he had contracted the deadly microbe, streptococcus, a bacteria that eats away at the sufferer from the inside, attacking the vital organs.

His housemate, Raymond Day, 35, also a drug user, was found dead on the kitchen floor of their flat in Carr Street, Avenham, on Sunday.

They had suffered similar symptoms, a severe rash, jaundice and were disorientated prior to death.

A mother-of-two, also from Avenham, who had been with Mr Preston on Saturday night, is in a critical condition at the Royal Preston Hospital.

Doctors are testing her for the killer bug.

Detective Sergeant John Crichton, of Preston CID, said: "The two men died almost straight away but the woman had been ill for a few days before she was taken to hospital.

"We would dearly like her to pull through but microbiologists have told me that the bacteria attached to the virus eats away at the flesh and no amount of drugs can help unless it is caught with a lot of antibiotics at an early stage."

He urged the dealer who supplied the heroin, thought to be from Liverpool, to come forward.

Det Sgt John Crichton said: "We do not know how many could be affected until we know where the drugs have come from.

"It could be isolated but could also affect a lot of people and we're concerned the drugs could be being circulated in the area. We would ask anyone who knows anything to come forward."

Any drug users with symptoms, including rashes or jaundice, should contact their GPs or attend hospital.

Staff at Lancashire Drug Action Team, a multi-agency group to help combat drug mis-use, have pledged to lay on extra supplies of the heroin substitute, methadone, for drug users.

Addicts still using the class A drug are advised to smoke rather than inject it.

Steve Gee, consultant in communicable disease control for the HPA, said: "As far as we are aware at the moment there are no other cases in the North West and we will be contacting all accident and emergency departments that cover the UK."

An investigation has been launched by the Health Protection Agency to see if there are any links between the two deaths and the woman.