HOUSTON (AP) - Rescuers began a block-by-block search of tens of thousands of Houston homes Thursday, pounding on doors and shouting as they looked for anyone - alive or dead - who might have been left behind in Harvey's fetid floodwaters, which have now damaged more than 87,000 homes and destroyed nearly 7,000 statewide.

Elsewhere, the loss of power at a flood-crippled chemical plant set off explosions and a fire, and the city of Beaumont, near the Texas-Louisiana line, lost its public water supply. The remnants of the storm pushed deeper inland, raising the risk of flooding as far north as Kentucky.

More than 200 firefighters, police officers and members of an urban search-and-rescue team fanned out across the Meyerland neighborhood for survivors or bodies. They yelled "Fire department!" as they pounded with closed fists on doors, peered through windows and checked with neighbors. The streets were dry but heaped with soggy furniture, carpet and wood.

"We don't think we're going to find any humans, but we're prepared if we do," said District Chief James Pennington of the Houston Fire Department.

The confirmed death toll stood at 39, though it is expected to rise. But by midday, the temporary command center in a J.C. Penney parking lot had received no reports of more bodies from the searches, which are expected to take up to two weeks.

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Unlike during Hurricane Katrina's aftermath in New Orleans, crews used GPS devices to log the homes they checked rather than painting neon X's on the outside. That avoided alerting potential thieves to vacant homes.

The blasts at the Arkema Inc. plant northeast of Houston also ignited a 30- to 40-foot flame and sent up a plume of acrid black smoke that stung the eyes and lungs. The blaze burned out around midday, but emergency crews held back because of the danger that eight other trailers containing the same compound could blow, too. No serious injuries were reported.

The latest statewide damage surveys revealed the staggering extent of the destruction caused by Harvey. The figures from the Texas Department of Public Safety indicated that nearly 50,000 homes sustained minor damage and 37,000 sustained major damage. At least 6,800 homes were destroyed.

In the Houston area, an estimated 136,000 structures, or 10 percent of all structures in the county database, were flooded, said Jeff Lindner, meteorologist for the Harris County Flood Control District.

About 325,000 people have already sought federal emergency aid in the wake of Harvey. More than $57 million in individual assistance has already been paid out, Federal Emergency Management Agency officials said.

Rescues continued apace, as did the search for shelter among people made homeless by the storm. Emergency officials reported 32,000 people in shelters across Texas.

The Harris County FEMA director said the agency was looking for ways to house people who lost their homes to Harvey. The priority is to get them into some form of temporary housing, with hotels being one option, he said.

"Right now nothing is off the table," Tom Fargione said. "This is a tremendous disaster in terms of size and scope."

Although it has been downgraded to a tropical depression, Harvey was still expected to dump heavy rain on parts of Louisiana, Tennessee and Kentucky through Friday. Forecast totals ranged from 4 to 8 inches (10 to 20 centimeters), with some places possibly getting up to a foot.

As the water receded in the nation's fourth-largest city, the greatest threat of damage shifted to a region near the Texas-Louisiana state line.

Some residents in Beaumont, Texas, began to get anxious after the city of nearly 120,000 lost water service when its main pump station was overwhelmed by the swollen Neches River. Officials said they were having difficulty bringing in enough bottled water to set up distribution stations because of flooded roads.

A procession of about 10 vehicles tailed a pickup towing a trailer packed with bottled water meant for emergency workers. The truck circled a downtown Beaumont block before Letorisha Hollier hopped out of the closest car.

"Give us a case!" Hollier shouted. Her persistence paid off. A firefighter handed her the water. She was the only tailgater to score a case.

Beaumont police spokeswoman Carol Riley said there were "some disturbances" in supermarkets because people were concerned about water.

The lack of water forced Baptist Beaumont Hospital to bring in ambulances and helicopters to move patients to other facilities, including some who had already been removed from flooded nursing homes. Hospital spokeswoman Mary Poole said other patients were able to be discharged.

In nearby Port Arthur, the Coast Guard used baskets and harnesses to pull people out of a neighborhood with chest-deep water.

Economists said the storm shut down everything from plastics plants to oil refineries to the Houston port - the second-busiest in the nation - which could affect the nation's economy.

With widespread reports of gas shortages, the head of the Texas agency that regulates the oil and gas industry urged drivers to wait three or four days to fill up their tanks. Panic buying is causing a run on gas and empty fuel pumps, Texas Railroad Commissioner Ryan Sitton said.

Energy Secretary Rick Perry said he would release 500,000 barrels of crude oil from an emergency stockpile in a bid to prevent gasoline prices from spiking.

Also Thursday, Houston public schools pushed back the start of classes by two weeks. The nation's seventh-largest district had been scheduled to reopen Monday but will now begin school on Sept. 11.

Health experts warned that sewage in the floodwater could make people sick and that mosquito populations could explode in the coming weeks because stagnant water offers abundant breeding grounds.

With temperatures likely to climb to the low 90s over the weekend, residents were warned about the dangers of heat exhaustion, especially for people who lost power or must toil outdoors.

Harvey initially came ashore as a Category 4 hurricane in Texas on Friday, then went back out to sea and lingered off the coast as a tropical storm for days, inundating flood-prone Houston.

The storm brought five straight days of rain totaling close to 52 inches (1.3 meters), the heaviest tropical downpour ever recorded in the continental U.S.