Houston, June 9 : At least 21 teenagers were injured after a ramp collapsed at a beachside city in the US state of Texas, authorities said. The incident took place at around 1 p.m. on Thursday at Stahlman Park in Surfside Beach, a small city about 96 km away from downtown Houston. The victims were aged from 14 to 18 years old, and they were from a summer camp, Xinhua news agency quoted Sharon Trower, public information officer for Brazoria County, as saying on Thursday night. Five of them were flown to hospitals in Houston by helicopter after the incident, while the others were taken by ambulance and private vehicles, she added. None of the injuries were expected to be life-threatening, according to local media reports. Footage from the scene showed a section of a wooden walkway ramp that had partially detached, falling on the grass below, ABC News reported. The cause of the ramp collapse is under investigation. /IANS