HONGYE VILLAGE, China - A quake-formed lake continued to swell yesterday even though soldiers used dynamite and antitank weapons to blow up boulders in a diversion channel to try to speed its drainage.

Authorities remained on alert after yet another aftershock jarred the Tangjiashan lake, which could flood more than 1.3 million people downstream if the water flow is not controlled.

Military engineers fired ammunition at huge rocks in a spillway dug to relieve pressure on the unstable barrier blocking the Tongkou River, the official Xinhua news agency reported.

Soldiers have also used three tons of dynamite over the last couple of days to blow up boulders and double the width of the channel to 33 feet, the report said.

The flow in the channel increased after more than 10 explosions, but it was not keeping up with the water gushing into the lake from the blocked river behind the dam.

Downstream

Yesterday, about 120 People's Liberation Army troops were sent to reinforce the operation to drain the lake, which formed when a landslide set off by the powerful May 12 earthquake blocked the flow of the Tongkou River.

Crews were deepening the diversion channel and digging a second spillway, Xinhua said.

More than 250,000 people downstream from Tangjiashan lake have been evacuated in recent weeks. Many were living in improvised camps on surrounding hillsides, surviving on instant noodles and suffering from heat, mosquitoes, and a lack of water for bathing.

Lu Raoxuang, a farmer in Hongye village about 30 miles downstream from Tangjiashan, said authorities forced him up a nearby hillside one day late last month when he returned home from tending his crops.

He said he was not even allowed to wash his face before evacuating his two-story brick and concrete home, which was badly damaged in the quake.

More aftershocks

Managing the lake is the latest challenge for the Chinese government, which is already shouldering the burden of caring for the five million left homeless by the disaster. The death toll in the May 12 quake climbed yesterday to 69,142, with 17,551 people still missing.

But efforts to control the lake have been hampered by aftershocks. A magnitude-5.0 quake rattled parts of the disaster zone yesterday afternoon, including the Tangjiashan lake. Rocks rolled down mountainsides and the dam shook, Xinhua reported, but it added that the dam held.

The 10-second temblor sent people in the hard-hit county of Wenchuan rushing out of shaking buildings and tents, Xinhua said. There were no reports of damage or casualties. Yesterday's aftershock followed one of the same magnitude the day before.