Beijing fire department says the students died in an accident during an experiment on wastewater treatment.

Three students have been killed in a laboratory blast at a Beijing university, the city’s fire department said.

“There was an explosion at the experimental site during a scientific research experiment” on wastewater treatment in the Environmental Engineering Laboratory, the Beijing Fire Department said on Wednesday.

“The accident caused three students to die,” it added in a statement posted on its social media account.

The incident occurred just after 9:30am local time (01:30 GMT) at the Beijing Jiaotong University in the western part of the city.

Videos of the scene, broadcast on local media, showed large flames and plumes of smoke pouring out of a low-rise building on the university campus.

Breaking: Explosion occurred in the laboratory of Beijing Jiaotong University while the students were carrying out the landfill leachate treatment test. #China pic.twitter.com/2AeQSRvM2H — Eva Zheng 郑怡斌 عائشة (@evazhengll) December 26, 2018

About 30 fire engines were sent to the scene and took nearly an hour to get the blaze under control.

Local authorities are launching an investigation into the cause of the incident.