A health watchdog has issued an urgent warning about a drug used to treat cancer patients following the deaths of two men in Birmingham.
Heartlands Hospital is carrying out an investigation
Baljit Sunner, 36, of Small Heath, and Paul Richards, 35, of Sutton Coldfield, died a day after treatment on 20 July.
It is believed they received five times the correct dose of amphotericin at the Heartlands Hospital.
The National Patient Safety Agency (NPSA) said it was essential healthcare staff were warned about the risks.
The hospital is now investigating the men's clinical care. A doctor and two nurses are believed to be not at work.
The NPSA said they were giving healthcare managers until 1 October to warn staff dealing with amphotericin.
Martin Fletcher, NPSA chief executive, said: "The agency is very concerned about the reports we've received in relation to intravenous amphotericin - we've issued an urgent warning to healthcare staff, giving them a month to carry out our recommendations.
"These are practical actions which, when implemented, will make it more difficult for mistakes to occur."
Hospital chiefs have said they are unable to comment on the situation until the investigation into the men's deaths has finished.