XI'AN, July 3 (Xinhua) -- Three workers were killed Saturday after a towering crane collapsed at a school building construction site in northwest China's Shaanxi Province, according to local authorities.

The accident happened around 1 p.m. when five people were working on the crane at the Shangluo Vocational and Technical College in Shangluo City, said a spokesman with the provincial emergency response office.

The operator of the crane and two workers died after falling about 30 meters, while two other workers survived the accident by climbed down from the tower, said the spokesman.

Another worker who suffered minor injuries was receiving treatment at hospital, he said.

The cause of the accident is under investigation.