BEIJING - CHINA said on Friday many of its schools were structurally unsafe more than seven months after a devastating earthquake, centred on southwestern Sichuan province, killed thousands of children under collapsed school buildings.

About 33.58 million sq m of primary and middle schools had safety problems, state media quoted Lu Yongxiang, vice-chairman of the National People's Congress (NPC) Standing Committee, as saying.

This was 2.5 per cent of the country's total school buildings, or the equivalent to 134 Bird's Nest stadiums in floorspace, he said, referring to the showcase stadium at the Beijing Summer Olympics.

'About 90 per cent of the dilapidated houses are in the country's central and western parts,' Mr Lu was quoted by China Daily as saying.

In Yunnan, neighbouring Sichuan and on the edge of the quake zone, 20 per cent of primary schools and 11 per cent of middle schools were 'not totally safe", according to the Ministry of Education.

And 85 per cent of those were of 'D' category, the most dangerous level.

An earthquake measuring 4.9 on the Richter Scale injured nine people early Friday in Ruili, a city in south-western Yunnan, when at least one old building collapsed, Xinhua news agency said.

The government estimates collapsed schools killed more than 19,000 children and teachers in the May 12 quake, nearly a quarter of the total deaths.

The deaths of children, many buried while nearby buildings withstood the tremors, have been the most controversial aspect of the disaster.

Beijing rapidly clamped down on reporting of the deaths and has been trying to silence grieving parents looking for redress in the court system.

'Most of the school buildings were built in the 1980s, when saving money was the priority and we didn't really give much thought to safety standards,' Wang Zhiren, a school representative in Nanba, one of the worst-hit townships, was quoted by the China Daily as saying.

Reconstruction of 3,340 schools in the quake zone is expected to be finished by September 2010. A local official told the newspaper a supervision mechanism has been set up to ensure quality. -- REUTERS