By Michael Bristow
BBC News, Beijing
Schools seemed to collapse more easily than other buildings
China has admitted that there could have been construction problems with some of the schools that collapsed during the Sichuan earthquake.
The admission follows an investigation into the building standards of schools and other structures that fell down.
Thousands of pupils were among nearly 90,000 people who died or are still missing following the quake in May.
Parents have demanded to know why so many schools collapsed, and want those responsible to be punished.
'Not necessarily reasonable'
Independent engineers and some local officials have previously said that they believe many of the schools that collapsed did so because they were badly built.
But Ma Zongjin's comments, made at a press conference on Thursday, are important because he is the chairman of the national committee set up by the government to investigate the earthquake.
In response to a question about the schools, he said: "The structures were not necessarily reasonable and the materials were not necessarily strong enough. Both are possibilities."
Officials have built temporary classrooms for surviving children
But he said some schools would have collapsed anyway because of the strength of the magnitude 8 earthquake that hit northern Sichuan Province.
"There were some buildings in the earthquake fault zone that were not able to resist the earthquake," he 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."
But schools did seem to collapse more easily than other buildings during the earthquake, which also left 5 million people homeless.
Some schools, such as Dujiangyan's Xinjian Primary School, were the only buildings to fall down in some areas.
From the very beginning, the parents of those children who died have wanted to know why schools appeared to collapse to such an extent.
Government officials promised an investigation while, at the same time, pressurising parents to keep their grief - and their anger - to themselves.
Mr Ma seemed to confirm parents' worst fears when he said that bad design and poor quality materials might have played a role in the schools' collapse.
"There were possibly some construction problems because we have built schools relatively quickly in recent times," he said.
The investigation is continuing, but Mr Ma seemed to downplay expectations that the probe would lead to those responsible being punished.
He said the aim of the investigation was to make sure new schools were built properly.