A center for delinquent boys was evacuated Friday night after 15 or more people were hospitalized with vomiting and nausea, authorities said.

David Morlan of the Boone County Emergency Management Agency said the cause of the sickness at the Woodward Academy has not been confirmed but a gas leak may be to blame.

Academy officials said the boys were moved to Woodward-Granger High School while a hazardous materials crew examined the building.

Mandy Moses, the academy's executive director, said staff and law enforcement were responding, but that she knew little else.

Morlan said that 15 to 20 young men in their late teens and early 20s were taken to local hospitals but did not have serious injuries. Jennifer Perry, an Iowa Methodist spokeswoman, estimated about 50 child and adult patients were taken to Iowa Methodist Medical Center and Blank Children's Hospital in Des Moines with the sickness.

The academy is about 30 miles northwest of Des Moines. It offers programs ranging from 90 days to 18 months and works with boys 12 to 18 years old.