A civilian helicopter was forced to make an emergency landing at around 11 am at a parking lot in Naidong village of Beijing’s Chaoyang district, injuring all of the 4 people onboard the aircraft, Beijing police said in a statement on its micro blog on Monday afternoon.

The police said that the accident was caused by mechanical malfunction and nobody was injured on the ground. Police officers and firefighters rushed to the accident site and shifted the injured to hospital. Authorities are investigating the accident’s cause, the statement said.