XI'AN - Sixteen students were injured Thursday in a stampede that occurred in an aquarium in Northwest China's Shaanxi province, local authorities said.

The incident occurred at the Xi'an Qujiang Aquarium around 1:37 pm, when dozens of students attempted to cram themselves into an elevator. A video recording shows one of the students falling down, with others subsequently piling up.

The injured students are being treated at a local hospital.

The primary school affiliated with Northwestern Polytechnical University said the students were sent to the aquarium for a field trip, as well as blamed the incident on the slow movement of the elevator.

Aquarium spokesman Yang Tao said the accident was caused by one of the students accidentally falling down, adding that the elevator was operating safely.

The incident is being investigated.