At least one person was killed and over 90 people were hospitalised in an outbreak of the legionella bacteria, which causes a type of pneumonia known as Legionnaire's disease in Portugal, authorities said Sunday.

The authorities are seeking out the source of the outbreak, which is focused on an area on the outskirts of the Portuguese capital of Lisbon, near the neighbouring city of Vila Franca, xinhua reported.

Of the 90 people hospitalised, a man aged 59 with a history of lung problems has died, and another 16-year-old was in critical condition.

Portugal's National Health Directorate has taken samples from the area's drinking water supply and ordered disinfection of water tanks.

The Secretary of State for Health has warned the population to avoid taking showers, using Jacuzzis or hot-tubs until the source of the infection has been identified.

Legionella is a waterborne bacterium that infects human when water droplets are inhaled into the lungs.