The Legionella bug contaminates water supplies and can be fatal

Walsall NHS Trust said the men, who work for the same company, may have been exposed to the bacteria in the Green Lane area of the town.

The company is co-operating with the investigation and all employees have been informed of the situation.

One man is now at home, but the second remains in New Cross Hospital.

Control measures

The Health and Safety Executive is also investigating the source of the outbreak.

The men are aged between 45 and 49 and come from Walsall and Wolverhampton.

Dr Sam Ramaiah, Walsall's director of public health, said the first case came to light three weeks ago and the second was identified earlier this week.

"The man who is still in hospital is in a critical but stable condition.

"He was in intensive care as he was quite ill, but are we more optimistic today (Friday).

"This is believed to be an occupational incident and residents living in the area are not considered to be at risk.

"We have initiated an investigation promptly and control measures have been put in place so that chances of further infection are minimised."

He added that it could be a "long time" before the source is confirmed.