NEW YORK — Four students were injured when a science experiment went wrong Wednesday at a school in the Bronx, CBS New York reports.

Officials at St. Catharine Academy in the Allerton section of the borough said the students were watching a demonstration by their teacher during first-period chemistry lab when they were singed.

"The teacher was doing a flame experiment. The flame got larger and several students were singed by the flame," school President Sr. Patricia Wolf said. "There were no hazardous materials involved."

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Assistant Fire Chief Joe Woznicki described it as a fire ball.

"There was an adverse chemical reaction to an average chemistry class experiment," Woznicki said.

Three students were slightly burned and another suffered respiratory problems.

The four sophomore girls were taken to the hospital and are expected to be OK. Two of the injuries are considered serious; the others minor.

The victims' parents were notified immediately and all other families received a text alert about the situation within an hour.

Wolf said the teacher involved has been with the school for three years, has a lot of experience in the chemistry lab and is distraught over what happened.

"It was an accident had happened and it was handled by the teacher appropriately," Wolf said. "I don't believe the teacher was reckless."

Hazmat crews responded to the school and determined there was no danger to other students and no contamination.

The school remains open and classes resumed during fourth period.

Nearly 500 students attend the school.