BEIJING - LIU Xiaoying fights back tears as she describes how the modern-looking primary school collapsed within seconds during the earthquake, killing her daughter and 125 other students, while other nearby buildings including a Qing-dynasty wall remained standing.

She is among a group of parents who have campaigned for months in the province of Sichuan, trying to get an official answer as to why the school gave way so easily. On Wednesday, nine of them were in the capital to demand that the central government investigate.

Questions about shoddy construction methods have become a flash point for government critics after the 7.9-magnitude quake killed nearly 70,000 people in May, including many students who were crushed to death when their schools fell.

'It has already been eight months since the earthquake, but there is still no news on what happened,' said Ms Liu, 35, as she stood outside the Communist Party's Central Committee for Discipline Inspection offices in downtown Beijing, waiting to deliver her petition. 'This will allow our children to rest in peace.'

She and eight other parents arrived from Sichuan this week and say they represent the families of 126 children who died when the three-story Fuxin No. 2 Primary School in Mianzhu city collapsed.

Ms Liu held out her mobile phone to show a picture of her 12-year-old daughter, who was killed. In the photo, Bi Yuexing - whose name is a combination of the Chinese characters for moon and star - wears a red cap and a red-and-white striped sleeveless top.

Her head is tilted slightly and she shows a charming smile.

'We are hoping that the party's central committee will investigate the question of building construction quality because we believe it had to do with the deaths of our children,' Ms Liu said.

'No other building around the area collapsed. The teachers' office didn't fall. Even a Qing dynasty mud wall didn't fall.'

The Qing dynasty ended in 1912, but Ms Liu did not say exactly when the wall had been built. Associated Press reporters who visited Mianzhu shortly after the quake saw many buildings near the school, including the teacher's offices and a dormitory, had survived intact.

Thousands of children are believed to have died in their classrooms during the quake, but there is no official toll. The government says 70,000 people died in Sichuan province and 7,000 classrooms were destroyed, but has avoided releasing a detailed breakdown of the fatalities.

While the government has promised an investigation and strict punishment for those responsible for the bad construction, there have been no public attempts to hold anyone to account. Marches and sit-ins by grieving parents held within months of the quake were broken up by police, with some parents briefly detained.

In September, a Chinese government scientist acknowledged that a rush to build schools in recent years likely led to construction flaws that caused so many of them to collapse - the first official admission that low building standards may have been behind the students' deaths. -- AP