Employees at the center realized there was a problem, evacuated the pool and had the children shower, said Capt. Mike Pfaltzgraff of the Anne Arundel County Fire Department. The chemicals did not cause injury to their skin, he said.
Patients were taken to Anne Arundel Medical Center in Annapolis, Baltimore Washington Medical Center in Glen Burnie, Johns Hopkins Hospital in Baltimore and Queen Anne's Emergency Center in Queenstown.
The patients were sent to different places so as not to overwhelm one hospital, Pfaltzgraff said.
The Fire Department received 911 calls just before 10 a.m. for complaints that multiple children were suffering from nausea and vomiting at Camp Letts.
Some parents arrived even before officials compiled a list of injured campers and alerted them; they gathered behind police officers as ambulances passed to take people to medical facilities.
"Not knowing if your kid is in there is really scary," said Heather Sandell of Annapolis, whose 12-year-old son, Jack, was attending the camp.
By midafternoon, 15 of the children were on their way home, said Jackie Dilworth, director of communications for YMCA of Metropolitan Washington. She said those remaining in the hospital into the evening were experiencing respiratory problems.
Camp Letts was founded in 1906 and moved to its present location on a 219-acre peninsula on the Rhode River in 1922.