CORPUS CHRISTI, Texas — As residents of the Texas Gulf Coast braced for days of "catastrophic" flooding from a weakened tropical storm Harvey, a law enforcement official confirmed the state's first fatality, a man trapped in his burning house during the height of the hurricane.

Late Saturday, a Houston official confirmed a death there due to flooding.

Aransas County Sheriff Bill Mills said that county's fatality was discovered Saturday in his home, which was destroyed by a fire as the Category 4 hurricane churned through the county.

The hurricane's toll may take time to determine, as Mills said 30 to 40 people remained unaccounted for as of Saturday evening. About 30 people were being treated for injuries in the county.

In Houston and Harris County, highways and major streets were starting to flood as up to 6 inches of rain fell on the city within three hours Saturday night.

The National Weather Service issued a Flash Flood Emergency for the Harris County area until after midnight.

Officials are urging people to stay off of the roads. The weather service said it has received multiple reports of water rescues in Harris County and nearby areas.

Two Aransas County municipalities, Rockport, with a population of 10,000, and nearby Port Aransas, took the brunt of the storm as it slammed into the coast late Friday.

At least 10 injuries were reported from collapsed roofs in Rockport, which is 25 miles northeast of Corpus Christi.

Nearby Port Aransas, with a population of 4,000, was particularly vulnerable perched on a narrow strip of Mustang Island, which sits at the entrance to Corpus Christi Bay. It registered the strongest wind gust of 132 mph from Harvey, according to the National Weather Service.

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The two towns, like dozens over others in the area, reported widespread damage as emergency teams searched for any survivors trapped in low-lying areas or collapsed buildings.

The National Oceanic and Atmospheric Administration (NOAA) Saturday tweeted a "geocolor loop" of the hurricane's movement Friday and Saturday, illustrating the size of the storm.

As of 10 p.m. CT, the National Hurricane Center reported that Harvey was centered 75 miles east-southeast of San Antonio. The storm was drifting east-northeast at 1 mph, and maximum sustained winds had dropped to 50 mph, with higher gusts.

On Saturday, officials throughout the region prepared for flooding. In the afternoon, the mayor of Rosenberg, a city about 35 miles southwest of Houston, ordered a mandatory evacuation for parts of the city due to potential flooding of the Brazos River, which hit a record high.

About 80 to 100 people are believed to have tried to ride out the storm in Port Aransas, which suffered extreme damage, including downed power lines, destroyed homes and businesses.

Port Aransas Mayor Charles Bujan said he and his first responders were still struggling to reach the island. Police officers and heavy equipment crews were attempting to enter the barrier island from the south, he said. As of Saturday morning, no fatalities or injuries had been reported there.

“The debris is so massive and the destruction is so massive, we haven’t been able to get in,” Bujan said.

Port Aransas City Manager David Parsons said they are mobilizing state police, troopers, National Guard and local law enforcement to conduct search-and-rescue efforts.

Early Saturday, Harvey’s destruction could be seen as far south as Corpus Christi, with downed street lights and trees blocking some downtown streets.

Fulton, a seaside community just north of Rockport, was a tangle of downed power lines, upended RVs and crushed homes. Downed trees blocked some roads in town; others were completely covered in floodwaters.

The roof from a nearby building was strewn across Texas State Highway 35, blocking one of the main entrances to Fulton and Rockport. In the middle of the night, as Harvey’s roars turned to quiet from the hurricane’s eye, some residents retreated to a local elementary school building.

“It was like being in another world,” said David Cameron, assistant chief of the Fulton Volunteer Fire Department, who helped rescue residents. “And there’s still a lot to do.”

Kevin Carruth, city manager of Rockport, said the courthouse had been hard hit, with a cargo trailer ending up halfway in the building. He said several people were taken to a makeshift hospital at the county jail for treatment after the roof of a senior housing complex collapsed.

The Austin American-Statesman reported from Rockport that the smell of gas filled the air at the Rockport-Fulton High School where the gymnasium was destroyed; the auditorium’s doors were caved in, and windows were shattered.

Rockport found itself on the deadly right-hand side of the eye of the storm as Harvey came ashore packing 130-mph winds.That location left it vulnerable to the dangerous storm surges as the winds piled up the Gulf waters and drove it ashore.

In Corpus Christi, city officials appealed to residents to reduce their use of toilets and faucets because of power outages at the city's wastewater treatment plants.

Texas Gov. Greg Abbott, speaking at the state's emergency operations center in Austin, reported 338,000 power outages statewide.

He also praised the "resilience" of those people who took the state's advice and evacuated the threatened areas for inland cities.

“It was so heartening to shake the hands of those evacuees as they got off those buses,” the governor told reporters. “They were what I call typical Texans. They were resilient, they were strong, but mostly, they were happy to be alive.”

Abbott says state military forces activated 1,300 service members to help with storm response. He said the Red Cross had opened 21 shelters holding about 1,450 people.

In the evening, the governor and his wife, Cecilia Abbott, helped serve dinner at a Red Cross shelter in Austin to people who had been evacuated because of the hurricane. He assured those at the shelter that the state is doing all it can to assist in the recovery effort.

In the Houston suburb of Cypress, a tornado touched down, damaging several homes and buildings but causing no apparent injuries, according to Harris County Sheriff Ed Gonzalez.

The storm dealt a glancing blow to neighboring Louisiana, where Gov. John Bel Edwards said the National Weather Service had confirmed a tornado touched down Saturday in the Cameron Parish town of Hackberry. Edwards says there were no reports of injuries or fatalities but there was “significant property damage.”

President Trump, who is at Camp David, met via teleconference with officials at the White House Saturday. He praised the "wonderful coordination" between federal, state and local governments in an early-evening tweet.

Although no longer a major hurricane, Harvey is far from a spent force. The National Weather Service says Harvey is expected to stall and spin for the next three to five days, delivering storm surges up to 12 feet in some areas and "catastrophic" flooding along the middle and upper Texas coast. It could also slip back into the Gulf and regenerate as a powerful storm and head up the coast toward Louisiana.

The Coast Guard, which urged Texas residents to stay off the water, reported rescuing at least 20 people in various incidents as Harvey came through the state, the Associated Press reported.

According to the AP, Capt. Tony Hahn, commander of the Corpus Christi sector, said Saturday that two helicopters rescued 18 people in various vessels: three from a fishing boat, four from a barge and 11 from two tugboats. Two people and their dog, who were stranded near Rockport, also were rescued and taken to a hospital.

The hurricane also left some 20,000 passengers stranded on four cruise ships that found conditions too dangerous to return to Galveston, KTRK-TV reported. The Carnival Valor and Carnival Freedom, which planned to return to Galveston on Friday, will instead head for New Orleans, according to the Houston Chronicle.

The Carnival Breeze stayed in Cozumel Friday night and was expected to leave for Galveston Saturday, while the Royal Caribbean Liberty of the Seas was expected to wait until Sunday to sail back to Texas, according to the report.

With Harvey hitting as a Category 4 hurricane, the record 4,324-day span between U.S. “major” hurricane (Category 3 and above) landfalls has ended, said University of Miami meteorologist Brian McNoldy. Before Harvey, the most recent major hurricane landfall had been Wilma in October 2005.

Harvey is only the fourth Category 4 or 5 hurricane to hit the U.S. since 1970, according to Colorado State University hurricane expert Phil Klotzbach. The other three were Hugo, Andrew and Charley.

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Contributing: Julie Garcia, Kirsten Crow, Rick Jervis, Doug Stanglin, Doyle Rice and Greg Hilburn of the USA TODAY NETWORK; KHOU-TV, Houston