(CNN) Three infants have died and five others have become ill from a waterborne bacterial infection at the neonatal intensive care unit of a Pennsylvania hospital, a spokesman said.

One baby is still receiving treatment and four others have recovered, said Geisinger Medical Center spokesman Joseph Stender.

All of the infected babies were born prematurely, Matthew Van Stone, director of media relations at the hospital, said in an email to CNN.

The hospital discovered the infection, caused by the pseudomonas bacteria, in July, according to Van Stone, and the deaths happened in the past two months. The July infection was in an older infant, who survived, he said.

The bacteria grows in water and is " found widely " in the environment, according to the Centers for Disease Control and Prevention.

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