The official Xinhua news agency said Sunday that the aircraft went down Saturday in fog and strong turbulence near the town of Yingxiu. The article gave no information on possible casualties, and said a search and rescue operation is under way.

The news agency also says the military has completed a project to drain backed-up water threatening more than a million people following the May 12 earthquake.

Xinhua said that by Saturday evening, the military had removed more than 135,000  cubic meters of mud and rocks that were blocking drainage of the swelling Tangjiashan lake.

People who lost children when the quake destroyed their schools, marked International Children's Day Sunday with grief and suspicions that shoddy construction had led to thousands of deaths.

In the town of Juyuan, about 100 grieving parents met at their children's collapsed middle school and called for a "blood debt" to be paid by officials responsible for the allegedly shoddy construction. About 900 students were buried in the school.

The officials Xinhua news agency says a Construction Ministry investigator found that steel rods used to reenforce the concrete at the Juyuan school were too thin.

Chinese President Hu Jintao marked Children's Day with a speech to a group of primary students at a tent school.

Mr. Hu told the children the Communist Party and Chinese government will rebuild their schools and give them a better learning environment.

Officials have increased the latest death toll to nearly 69,000. About 20,000 others are reported missing.