Calcutta, Aug. 21: A waterslide at an amusement park here caved this afternoon with about 20 children on it after some of the revellers allegedly overpowered a gatekeeper and barged into it though only one person is allowed at one go.

A portion of Body Slide, the 76-metre-long serpentine slide inside Wet-O’ Wild at Nicco Park, broke down unable to bear the weight of too many people.

The children, aged between nine and 18, fell from a height of around 13 feet on grassland. All of them suffered injuries and at least three have broken bones.

Nicco Park, located in the tony east Calcutta exurb of Salt Lake, is a popular destination for both residents and those visiting the city — either on holiday or on business. The amusement park, which lies barely a kilometre away from the IT hub at Salt Lake’s Sector V, regularly attracts visitors from neighbouring Bihar, Odisha and Jharkhand.

Eyewitnesses said the people on the slide even stood up and danced. The security guards, outnumbered to handle the rush, hardly showed any initiative to stop the revellers, alleged victims.

“I had come down only few metres when I found some people had stopped on the slide in front of me. I rammed into them and stopped. Within a few seconds, several others rammed into me from behind,” said Sikander Ahmed, a Class IX student.

Kamal Hasan, 13, another injured, said that the security guards did not stop anyone from boarding the slide, though it had already been packed with people. “It was a free-for-all. There was no regulation,” said Hasan, who broke his pelvis and also suffered injuries on his spine.

Nicco Park authorities said today there were about 40 security guards in Water Park, while about 1,500 people bought tickets since 3pm.

The authorities said the portion of the slide that broke was about 13ft above ground. “The highest point is 36ft. It broke down at a point 13ft above ground,” said Rajesh Raisinghani, associate vice-president, Nicco Park.

The injured also alleged that they had to hire taxis on their own to reach hospital though Raisinghani said that they arranged for the medical treatment of the injured.

The authorities said unruly revellers overpowered the security guards. “There were six security personnel but about 20 people together pushed them aside and entered the ride,” said Raisinghani.