Nine people have died after the roof of a sports hall collapsed at a sports hall in northeastern China, and two are still trapped under the rubble, the official Xinhua news agency said on Monday, according to AFP.

The building collapsed at 3:00 p.m. local time (07:00 GMT) on Sunday in Qiqihar, Heilongjiang province, Xinhua reported.

As of 03:00 Monday (19:00 GMT Sunday), 13 people had been pulled from the rubble, “three of whom were pulled out without any signs of life, and another six died after ineffective medical treatment,” the agency said.

Footage from the national television company CCTV showed that the roof of the gym had completely collapsed and rescuers were digging under the rubble.

“A search and rescue operation involving nearly 160 firefighters and 39 fire trucks has been launched,” CCTV reports.

According to initial reports from an investigation by Xinhua, workers constructing the building used perlite, a form of volcanic glass, for the roof.

Heavy rain caused the silicon-based material to expand, causing the roof to crack and then collapse, the agency said, adding that construction company officials were taken into custody.

Accidents related to construction are common in China, where there is a certain tolerance for safety regulations, the enforcement of which remains insufficient.

In 2015, a powerful explosion at a chemical warehouse in Tianjin killed at least 165 people, which became one of the worst disasters of its kind, AFP recalls.