Workers at a Bradford factory which saw a case of the killer disease anthrax are being warned to be on the alert as they return to work.

Health and Safety Executive (HSE) officials have allowed the processing department to re-open at Joseph Dawson's cashmere factory, off Leeds Road, Bradford.

Factory employee Fazal Mahmood Dad, 35, is now out of hospital after receiving treatment for the skin form of anthrax.

And a spokesman for the HSE said samples taken from around the factory had not revealed the source of the anthrax infection.

More inquiries were continuing to try to pinpoint where the deadly bacteria had come from. Anthrax is a bacterium which can survive in spores within animal hair or dust for many years. It cannot spread from person to person.

The HSE spokesman said: "We are stressing the importance to employers and employees to look for signs of infection. No signs of infection have emerged anywhere and there are no signs that the area poses any particular risk providing people are vigilant." HSE inspectors are talking to staff at the factory.

Mr Dad, a father-of-five of Thornbury, first noticed a small spot on his arm after work. It worsened over a couple of days and he was admitted to Bradford Royal Infirmary. Doctors there quickly diagnosed the skin form of anthrax, although a case has not been confirmed in the UK since 1995. There were only four confirmed cases of the disease in the country between 1990 and 1998.

If people breathe in the spores which carry the active bacteria, and get the pulmonary form of the disease, it is almost invariably fatal.