Chinese media reported Monday that at least 11 people, mostly young students, lost their lives after the roof of a gymnasium came down crashing on a girl’s volleyball team in the industrial province of Heilongjiang.

The media reports suggest that only eight out of 19 people survived who were inside the gym. The owners of the place were detained by the police at a local construction company.

The roof collapse was reported at 2:56pm Sunday, according to the provincial fire and rescue department. 

They have been allegedly dumping a form of volcanic glass called pertile on the roof of the gym while working on an adjacent building project, the Chinese media said.

According to China National Radio, the coaches of the middle school’s girls’ volleyball team were heard calling out the students’ names as rescue teams were removing the debris.

Parents criticised the school officials, saying “there had been a lack of proper communication on the rescue effort, which stretched until Monday morning.”

Under the influence of rainfall, the perlite soaked up water and gained weight, resulting in the roof collapse, according to Xinhua.

“They tell me my daughter is gone but we never got to see the child. All the children had their faces covered with mud and blood when they were sent to the hospital. I pleaded, please let me identify the child. What if, that wasn’t my child?” one man said in a video that was widely shared on social media.

“What have [the authorities] been doing four, five, or even six hours after the children were sent to the hospital? … Doctors are not communicating with us about how the rescue is going.

“We have elderly people at home, we need to [help them] be mentally prepared. There are doctors, police officers, and other government officials here. But we have not heard anything from you,” he said.