The probe came after parents of thousands of students who died in the quake or who still remain unaccounted for demanded to know why so many schools came down during the disaster, the BBC reported.

The parents want those responsible for the havoc punished.

Ma Zongjin, chairman of a government committee investigating the issue, told reporters Thursday, "The structures were not necessarily reasonable and the materials were not necessarily strong enough. Both are possibilities."

But he also said some of the schools would have come down regardless because of the magnitude 8 temblor, the report said.

"There were some buildings in the earthquake fault zone that were not able to resist the earthquake," Ma said. "So it didn't matter whether it was a building for children, a school, a government building or a residential block. They were all destroyed."

However, the report said in some areas, school buildings were the only structures to come down.

"There were possibly some construction problems because we have built schools relatively quickly in recent times," Ma said.