Norwegian authorities said Tuesday they were trying to identify the source of water contamination that has sent dozens of people in southern Norway to the hospital.

Since Thursday, 55 people — including 13 children — from Askoey, an island north of Bergen, have been hospitalized following the contamination. All have been discharged. Norwegian news agency NTB reported that in all, some 2,000 people had fallen sick.

A 1-year-old child on the island died last week of an infection in the digestive tract, but it was not clear whether it was linked to the contamination.

"None of the patients are critically ill," said Oeyvind Kommedal, a doctor with the Haukeland university hospital that carried out laboratory tests. "We have a good control of the situation."

He said tests showed that the bacteria Campylobacter has been found in 36 cases.

On Monday, Baard Espeli, deputy mayor of the municipality of Askoey, also said that E. coli was found in a reservoir that supplied part of the area's drinking water.

Espeli said that reservoir has been closed, but it remains unclear how the bacteria contaminated it in the first place.

Campylobacter is one of the main causes of diarrheal diseases and is considered the most common bacterial cause of human gastroenteritis. Infections are generally mild, but can be fatal among very young children and the elderly.

Most E. coli strains are harmless, but some can cause diarrhea, urinary tract infections, respiratory illness and pneumonia.