Shenzhen authorities said 28 people were injured in a rollercoaster crash at the Happy Valley theme park in Nanshan district, and 17 are still in hospital.

Officials on Sunday released details of the incident, which took place at about 6.30pm on Friday. They said a train – carrying 22 people – suddenly plummeted while it was ascending and collided with another train on the platform.

Nanshan district authorities said four people remain in intensive care with brain injuries or pelvic fractures. They are said to be stable. Others suffered minor fractures and soft tissue injuries.

Shenzhen Happy Valley, which has been ordered to suspend operations and carry out thorough safety checks, said the park will remain closed until further notice.