A gas line explosion at a New York high school on 20 August injured three construction workers, one critically, authorities said.

The explosion occurred in the early evening hours at John F Kennedy High School in New York's Bronx borough while construction work was going on in a sixth-floor laboratory, a police spokesman said.

"I didn't think it was a thunder storm because the whole house shock like it was going to fall down completely," said Lorsea Varado, a resident of the Bronx who lives nearby.

A fire department spokesman said all three of the injured were taken to Jacobi Medical Center, two with non-life-threatening injuries. The police spokesman said there was damage to two non-load-bearing walls. The New York school year starts on 9 September.