More than 1 million people may have to evacuate dozens of villages in a Sichuan province valley if an earthquake-spawned lake threatens to burst and flood the region, an emergency official warned Friday.

Authorities were preparing to run a drill starting Saturday to ensure 1.3 million people in the Mianyang region can get out quickly if the lake breaks through the wall of debris clogging a river.

An official with the press office of Mianyang City Quake Control and Relief Headquarters, who would giver only her surname of Chen, said a report Friday by the official Xinhua News Agency that a mass evacuation already had been ordered was wrong.

"People will only be evacuated in case of actual collapsing of the whole bank," Chen told The Associated Press.

Chinese troops were still working to drain the Tangjiashan lake, which formed above Beichuan town after a quake-triggered landslide blocked a river. There was no sign that the dam formed by a landslide caused by the May 12 quake was about to burst on Friday, though officials say it could do so in coming days.

Chen said 197,500 people in the valley were being moved to higher ground — about 30,000 more than previously announced.

On Saturday, officials will start a three-day drill that will test government communications systems to ensure that any evacuation order — if it comes — quickly filters down to residents in the valley.

Soldiers were using 40 heavy earth-moving machines to dig drainage channels. Officials quoted in state media have not said how long the work would take.

The confirmed death toll from China's worst quake in three decades was 68,858, the government announced Friday, an increase of about 350 from a day earlier. Another 18,618 people were still missing.

In the chaos after the magnitude 7.9 earthquake, which made 5 million homeless, many survivors were separated from their families.

Thousands of children and parents who had been separated have been reunited, officials said Friday, while the government has been inundated with requests from families to adopt other children orphaned by the disaster.

Social workers have helped bring together more than 7,000 children and their families since the earthquake struck Sichuan province May 12, said Ye Lu, director of social welfare at the provincial Civil Affairs Department.

"A little more than 1,000 children remain unclaimed or orphaned," Ye said.

The government has been overwhelmed with calls seeking to adopt those children, Ye said.

"We are still getting thousands of calls per week asking about how to adopt, but we are still hoping to find the parents of these 1,000 kids," he said.

Also on Friday, government officials in Tokyo said Japan would not use military planes to deliver relief goods to China after Beijing voiced uneasiness over the idea.

China had been in talks with Tokyo about using Japanese military planes to deliver aid, which could have become the first significant military dispatch between the two nations since World War II.

But Japanese Chief Cabinet Secretary Nobutaka Machimura said Tokyo would not insist on using the military.

Japan invaded China and conquered large parts of it in the 1930s before being defeated by the Allies in 1945, and many Chinese still strongly resent Japan for its military aggression.