A weekend for winding down summer at the Jersey Shore turned into a mass casualty scene Saturday evening when at least two decks on a three-story rental home collapsed onto each other, the authorities said.

At least 21 people were injured in the episode, including an unspecified number of firefighters who had come to Wildwood, New Jersey, for the annual New Jersey Firemen's Convention, according to hospital and local officials.

Two of the victims were characterized as trauma patients, with one airlifted by helicopter and a second scheduled to be transferred by ambulance to hospitals in the area, said Susan Staeger, a spokeswoman for Cape Regional Health System in Cape May Court House, New Jersey.

Nineteen people were treated at the hospital and discharged, according to Staeger, who said three of them were children. She did not have more information on the condition of the trauma patients.

Ernie Troiano Jr., Wildwood's mayor, said in an email Saturday night that firefighters were among those injured. He did not have immediate details on the number or the extent of their injuries.

The episode happened two blocks from a popular boardwalk at about 6 p.m., with photos showing a mangled pile of wood and other debris.

"It was horrible," said Christian Cruz, an employee at La India, a nearby bodega.