(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 heavily damaged more than 37,000 homes and destroyed nearly 7,000 statewide.

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 31, 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.

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

Elsewhere, the loss of power at a chemical plant set off explosions that prompted a public health warning. The blasts at the Arkema Inc. plant northeast of Houston also ignited a 30- to 40-foot flame and sent up a plume of smoke that the head of the Federal Emergency Management Agency initially described as "incredibly dangerous."

FEMA later backed away from that statement, saying that Administrator Brock Long spoke out of an abundance of caution. An Environmental Protection Agency analysis of the smoke showed that it posed no immediate threat to public health, the agency said.

The French operator of the plant feared that up to eight more chemical containers could burn and explode.

The latest damage surveys revealed the staggering extent of the destruction. The figures from the Texas Department of Public Safety did not include the tens of thousands of homes with minor damage.

About 32,000 people were in shelters across the state, emergency officials reported.

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

"Right now nothing is off the table," Tom Fargione said Thursday. "This is a tremendous disaster in terms of size and scope. I want to get thinking beyond traditional methodologies you've seen in the past."

As the water began to recede in the nation's fourth-largest city, the threat of major damage from the storm shifted to a region near the Texas-Louisiana state line.

Beaumont, with a population of nearly 120,000, and nearby Port Arthur struggled with rising water after being pounded with what remained of the weakening storm. Beaumont lost water service after its main pump station was overwhelmed by the swollen Neches River. That forced Baptist Beaumont Hospital to airlift nearly 200 patients to other facilities.

Port Arthur found itself isolated as floodwaters swamped most major roads out of the city. More than 500 people - along with dozens of dogs, cats, a lizard and a monkey - took shelter at the Max Bowl bowling alley, general manager Jeff Tolliver said.

"The monkey was a little surprising, but we're trying to help," he said.

To help with the recovery, about 10,000 more National Guard troops are being deployed to Texas, bringing the total to 24,000, Gov. Greg Abbott said.

Floodwaters also toppled two oil storage tanks in South Texas, spilling almost 30,000 gallons (114,000 liters) of crude. It was not immediately clear whether any of the spilled oil was recovered. More damage to the oil industry infrastructure is expected to emerge as floodwaters recede.

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.

Macroeconomic Advisers, a forecasting firm, calculates that economic damage could shave between 0.3 and 1.2 percentage points off the nation's economic growth in the July-September quarter. The economy had been expected to grow at an annual rate of about 3 percent from July through September.

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.

For much of the Houston area, the rain had passed. But with temperatures likely to climb in 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.

Houston's two major airports were slowly resuming full service. Limited bus and light rail service had also been restored, as well as trash pickup.

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.

Harvey's five straight days of rain totaled close to 52 inches, the heaviest tropical downpour ever recorded in the continental U.S.