HOUSTON >> Houston officials will open two or three more mega-shelters to accommodate people who continue to arrive at the overflowing George R. Brown Convention Center seeking refuge from Harvey’s record-breaking flooding, Mayor Sylvester Turner said today.

The center already held more than 9,000 people, almost twice the number officials originally planned to house there, Turner said.

“We are not turning anyone away. But it does mean we need to expand our capabilities and our capacity,” Turner said. “Relief is coming.”

More than 17,000 people have sought refuge in Texas shelters and that number seemed certain to increase, the American Red Cross said.

City officials have made a formal request with the Federal Emergency Management Agency for more supplies, including cots and food, for additional 10,000 people, which he hopes arrive no later than Wednesday, the mayor said.

Also today, the Houston Chronicle reported that a city police officer drowned in his patrol car as he was driving to work. The newspaper, citing three unidentified department officials, said the 30-year officer was heading to work Sunday when he became trapped in his car in high water on Interstate 45 in north Harris County.

Mayor Sylvester Turner and Police Chief Art Acevedo said today they were aware of the report but would not confirm it.

The storm continued to take a toll even as the weather outlook improved slightly.

A pair of 70-year-old reservoir dams that protect downtown Houston and a levee in a suburban subdivision began overflowing today, adding to the rising floodwaters from Harvey that have crippled the area after five consecutive days of rain that set a new U.S. record for rainfall for a tropical system.

Brazoria County authorities posted a message on Twitter warning that the levee at Columbia Lakes south of Houston had been breached and telling people to “GET OUT NOW!!” Brazoria County Judge Matt Sebesta said residents were warned that the levee would be overtopped at some point, and a mandatory evacuation order was given Sunday.

pic.twitter.com/sUTyXBzer9

— Brazoria County (@BrazoriaCounty) August 29, 2017

Engineers began releasing water from the Addicks and Barker reservoirs Monday to ease the strain on the dams. But the releases were not enough to relieve the pressure after one of the heaviest downpours in U.S. history, Army Corps of Engineers officials said. Both reservoirs are at record highs.

The release of the water means that more homes and streets will flood, and some homes will be inundated for up to a month, said Jeff Lindner of the Harris County Flood Control District.

The county is trying to determine where the water will go, Lindner said.

A weather station southeast of Houston reported 49.32 inches of rain as of this morning, according to the National Weather Service. That breaks the previous record of 48 inches set in 1978 in Medina, Texas, by Tropical Storm Amelia.

Already 14 sites in Houston have recorded more than 40 inches of rain and 36 different locations have recorded more than 3 feet.

Although forecasters had feared that another 2 feet could fall in some places, it appeared that the outlook had improved somewhat today. The weather service said the amount of rain falling in the Houston area would be 2 to 3 inches, perhaps a little less in Houston proper, as the storm moved east.

But southeastern Texas and southwestern Louisiana still would see “relentless torrential rains,” with another 6 to 12 inches of rain across the upper Texas coast through Friday as Harvey continues to move slowly east over the Gulf of Mexico maintaining tropical storm force winds of 45 mph, the National Hurricane Center said.

It is expected to make landfall again Wednesday morning, probably in southwestern Louisiana

Calls for rescue have so overwhelmed emergency teams that they have had little time to search for bodies. And officials acknowledge that fatalities from Harvey could soar once the floodwaters start to recede from one of America’s most sprawling metropolitan centers.

More than four days after the storm ravaged the Texas coastline as a Category 4 hurricane, authorities had confirmed only three deaths — including a woman killed Monday when heavy rains dislodged a large oak tree onto her trailer home in the small town of Porter. But unconfirmed reports of others missing or presumed dead were growing.

“We know in these kinds of events that, sadly, the death toll goes up historically,” Houston Police Chief Art Acevedo told The Associated Press. “I’m really worried about how many bodies we’re going to find.”

One Houston woman said Monday that she presumes six members of a family, including four of her grandchildren, died after their van sank into Greens Bayou in East Houston.

Virginia Saldivar told The Associated Press her brother-in-law was driving the van Sunday when a strong current took the vehicle over a bridge and into the bayou. The driver was able to get out and urged the children to escape through the back door, Saldivar said, but they could not.

“I’m just hoping we find the bodies,” Saldivar said.

Houston emergency officials could not confirm the deaths.

A spokeswoman for a Houston hotel said one of its employees disappeared while helping about 100 guests and workers evacuate the building.

The disaster is unfolding on an epic scale, with the nation’s fourth-largest city mostly paralyzed by the storm that parked itself over the Gulf Coast. With nearly 2 more feet of rain expected on top of the 30-plus inches in some places, authorities worried the worst might be yet to come.

Harvey kept drenching Houston and the surrounding area. Rain fell today at about half an inch per hour over Harris County — home to Houston — and up to 2 inches per hour to the east.

The Houston metro area covers about 10,000 square miles, an area slightly bigger than New Jersey. It’s crisscrossed by about 1,700 miles of channels, creeks and bayous that drain into the Gulf of Mexico, about 50 miles to the southeast from downtown.

Forecasters expect the storm to linger over the Gulf before heading back inland east of Houston sometime Wednesday. The system will then head north and lose its tropical strength.

It could creep as far east as Mississippi by Thursday, meaning New Orleans, where Hurricane Katrina unleashed its full wrath in 2005, is in Harvey’s path. Foreboding images of Harvey were lighting up weather radar screens early today, the 12th anniversary of the day Katrina made landfall in Plaquemines Parish.

Rescuers meanwhile continued plucking people from inundated Houston neighborhoods. Mayor Sylvester Turner put the number by police at more than 3,000. The Coast Guard said it also had rescued more than 3,000 by boat and air and was taking more than 1,000 calls per hour.

Associated Press writers Frank Bajak and Michael Graczyk in Houston, Diana Heidgerd and David Warren in Dallas, Seth Borenstein in Washington and Tammy Webber in Chicago contributed to this report.