Health officials confirmed today that two patients have contracted Legionnaires' disease at a hospital which has recently been criticised for blood-splattered equipment and an unusually high death rate among patients.

Both patients were at Basildon University Hospital in Essex when they began to show signs they were affected by the bacteria legionella.

A spokeswoman said the patients, who were staying in different parts of the hospital, have responded to antibiotic treatment but one of them is still in a critical condition.

Hospital chief executive Alan Whittle said: "We have continued to be vigilant and no further suspected cases have been identified.

"Based on the results of laboratory tests of water samples, we accept that the hospital is the probable source of the infection, despite our determined efforts to minimise the known risks of legionella.

"We do take the legionella risk extremely seriously. We test any patient with suspicious respiratory problems and we regularly test our water system for the bacteria."

The spokeswoman added that the last outbreak of the disease was in 2007.

Whittle said: "Experts agree that the legionella bacteria is a common risk in large buildings with an extensive plumbing system.

"We accepted some time ago the advice of experts that we will never be able to completely eradicate the bacteria, but we have worked hard to minimise the risk.

"I would like to take this opportunity to reassure patients that the hospital is safe and the risk of contracting Legionnaires' disease is extremely low."

Legionnaires' disease is a potentially fatal lung infection caused by the bacteria legionella. It is contracted when small droplets of contaminated water are breathed in.

Symptoms of the disease include headaches, fever, chills, muscle pain and coughs. It is estimated 10% of people who contract Legionnaires' disease will die from complications arising from infection.

The hospital spokeswoman said that the health and safety executive is now investigating the outbreak.

In November, inspectors from the Care Quality Commission criticised Basildon and Thurrock University Hospitals NHS Foundation Trust after they found blood stains on floors and curtains, blood splattered on trays used to carry equipment and badly soiled mattresses in the A&E department with stains soaked through.

Inspectors also found equipment being used repeatedly that should only be used once and resuscitation room equipment that was past its use-by date.

Other items found at the trust included blood pressure cuffs stained with blood, suction machines contaminated with fluid inside and out and apparent mould.

However, on December 23, the watchdog said that hygiene standards were improving and that the trust has taken action to address concerns about infection prevention and control.