LUOSHUI TOWN, China — Troops dug burial pits in this quake-shattered town and black smoke poured from crematorium chimneys elsewhere in central China as priorities began shifting Thursday from the hunt for survivors to dealing with the dead. Officials said the final toll could more than double to 50,000.

As the massive military-led recovery operation inched farther into regions cut off by Monday's quake, the government sought to enlist the public's help with an appeal for everything from hammers to cranes and, in a turnabout, began accepting foreign aid missions, the first from regional rival Japan.

Millions of survivors left homeless or too terrified to go indoors faced their fourth night under tarpaulins, tents or nothing at all as workers patched roads and cleared debris to reach more outlying towns in the disaster zone.

Health officials said there have been no outbreaks of disease so far, with workers rushing to inoculate survivors against disease, supply them with drinking water, and find ways to dispose of an overwhelming number of corpses.

"There are still bodies in the hills, and pits are being dug to bury them," said Zhao Xiaoli, a nurse in the ruined town of Hanwang. "There's no way to bring them down. It's too dangerous."

Troops in the town of Luoshui in a quake-ravaged area used a mechanical shovel to dig a pit on a hilltop. Two bodies wrapped in white sheets lay beside it. Down the hill sat four mounds of lime.

In a sign of nervousness, 50 troops lined the road outside Luoshui. Five farmers watched them dig the burial pit, after performing brief funerary rites. Local police detained an Associated Press reporter and photographer who took photos of the scene, holding them in a government compound for 3 1/2 hours before releasing them without explanation.

Across the quake zone in Dujiangyan, troops in face masks collected corpses and loaded them onto a flatbed truck. Thick black smoke streamed from the twin chimneys of the town's crematorium. when it was reached by an AP photographer, indicating the threat to the structure had likely passed

People trying to hike into Wenchuan walked on top of the dam as water spilled from an outlet, lowering levels in the reservoir and alleviating pressure on the dam.

Just behind the dam, soldiers set up a staging area preparing speed boats to lower into the reservoir and ferry soldiers in lifejackets, engineers and medical staff up river to Yingxiu, a town flattened by the quake.