KAUNAS, Lithuania — Suspected over-chlorination of a pool in Kaunas left swimmers feeling nauseous after taking a dip at the Oazė wellness center Saturday and sent two, a fifteen-year-old boy and 45-year-old man to the hospital.

While the man was released Sunday, the boy remains in the hospital breathing only through artificial means. Chlorine poisoning severely irritates the respiratory system.

The center is run by the Lithuanian company Impuls, which operates fitness centers throughout the country. Impuls said it was unsure if over-chlorination occurred and is consulting independent experts and the pool manufacturer to investigate. Meanwhile a test by public health officials showed that despite the symptoms of swimmers, chlorine was not at an unreasonable level, although they warned that chlorine levels can fluctuate rapidly.