Beijing  - Mourning has increasingly turned into anger by some of the survivors of this month's earthquake in south-western China.

Hundreds of parents of perished children recently marched through the town of Mianzhu in the afflicted province of Sichuan. They carried photographs and banners decrying the deaths of their children in collapsed schools.

Substandard construction is blamed for the agony of those parents after many of the 7,000 flattened school buildings in the region simply crumbled like houses of cards while thousands of pupils were inside.

Local authorities struggling to deal with the aftermath of the magnitude-8 May 12 quake have found themselves increasingly facing the scorn of parents.

In an unusual gesture, Mianzhu's Communist Party chief fell to his knees before a procession of parents to plead with them to end their protests about their children's deaths.

"Their hearts are broken, and they demand an explanation," the party chief, Jiang Guohua, said, according to China's state-run news agency Xinhua.

Many parents blamed greedy party cadres and construction companies for the high number of deaths among their children, charging them with skimping on quality construction to line their own pockets.

The vice inspector of the Sichuan education department, Lin Qiang, admitted that educational officials had left open "loopholes for corruption."

His department, meanwhile, admitted that shoddy construction and aged buildings had been at least partially responsible for the schools' collapse.

A Beijing-based academy for building security has dispatched about 60 experts to the region to examine and investigate the ruins.

"A fundamental rule should be that school buildings have a higher construction standard against earthquakes than other buildings," said Wang Xuming, a spokesman for Beijing's Education Ministry.

It took a mere 10 seconds for the quake to level Fuxin Elementary School Number 2 in Mianzhu, during which 127 schoolchildren lost their lives.

But surrounding houses, some of them dating back to the 1960s, were left unscathed.

Up to 10,000 schoolchildren were killed in the quake by some estimates among a total confirmed death toll of 68,858. The government said another 18,618 people are missing.

Experts identified rigid and non-reinforced concrete as the principal building faults in schools.

One of the first foreign experts to examine the earthquake zone's school buildings was Japanese-American engineer Kit Miyamoto.

Ill-cured concrete, he said, was identified as the "killer culprit" that caused the destruction of Juyuan secondary school in the heavily afflicted town of Dujiangyan.

Erected in 1996, the school collapsed and killed an estimated 700 of its 1,000 students.

The former school now resembled a field of ruins, he said.

Miyamoto wrote in his report that concrete ceilings in the school building were braced by relatively weak brick sidewalls and thus lacked stable construction overall, "turning them into "killers." (dpa)