(CNN) -- A stampede at an elementary school in central China killed four students and injured more than 10 others Wednesday morning, authorities said.
The cause of the crush at Qinji Elementary School in Hubei province is still under investigation, the state-run news agency Xinhua said in a short report.
State-run broadcaster CCTV reported that it happened after an iron gate at the students' dormitory failed to open. As the children were unable to exit through the gate, a large number of people built up against it, CCTV said.
The pressure caused the gate to collapse, resulting in the stampede, the broadcaster reported. It wasn't immediately clear why the gate wouldn't open.
A photograph carried by Xinhua showed one of the students injured in the crush, Zhang Jiali, receiving treatment on a bed in a hospital in Laohekou City in Hubei. The child was still dressed in a purple jacket and stripy, wooly leggings.
A total of 11 children were injured in the stampede, authorities in Laohekou said on their microblog account.
A number of stampedes have taken place at Chinese schools in recent years.
In 2009, eight students were killed and 26 were injured in an incident at a middle school in Hunan province.
And in 2006, a stampede was reportedly set off in a middle school in Sichuan province by a student who stopped to tie shoelaces on a staircase. The resulting crush killed eight people and injured 27.
CNN's CY Xu in Beijing and Tim Schwarz in Hong Kong contributed to this report.