HOUSTON (AP) -Houston Mayor Sylvester Turner says police have rescued 1,000 people in the last eight hours, bringing the total number of people rescued to 3,052 since Tropical Storm Harvey inundated many parts of Houston.

At a news conference Monday evening, Turner also said that at least 150 critical rescue requests were still pending.

The U.S. Coast Guard said that on Monday it had rescued more than 3,000 people by boat and air and that it is getting over 1,000 calls per hour.

Officials says that in Houston, more than 100,000 customers remain without power and that number remained steady on Monday as work crews have had difficulty getting into areas due to flooding.

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The disaster unfolded on an epic scale in one of America’s most sprawling metropolitan centers. 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.

The flooding was so widespread that the levels of city waterways have either equaled or surpassed those of Tropical Storm Allison from 2001, and no major highway has been spared some overflow.

The city’s normally bustling business district was virtually deserted Monday, with emergency vehicles making up most of the traffic. Most traffic signals were out and most businesses closed.

Elsewhere, water gushed from two reservoirs as officials sought to release pressure on a pair of 70-year-old dams that protect downtown Houston. Water was at risk of spilling around the sides of the barriers, which have a long history of seepage. The move would help shield the business district from floodwaters, but it could also flood thousands more homes.

Meanwhile, rescuers continued plucking people from the floodwaters – at least 2,000 so far, according to Acevedo. At least 185 critical rescue requests were still pending on Monday morning, he said.

Rescuers were giving priority to life-and-death situations, leaving many people to fend for themselves.

Chris Thorn was among the many volunteers still helping with the mass evacuation that began Sunday. He drove with a buddy from the Dallas area with their flat-bottom hunting boat to pull strangers out of the water.

“I couldn’t sit at home and watch it on TV and do nothing since I have a boat and all the tools to help,” he said.

They got to Spring, Texas, where Cypress Creek had breached Interstate 45 and went to work, helping people out of a gated community near the creek.

“It’s never flooded here,” resident Lane Cross said from the front of Thorn’s boat, holding his brown dog, Max. “I don’t even have flood insurance.”

Houston’s 911 system has received 75,000 calls since Harvey inundated the city, including 20,000 just since late Sunday. The city normally averages 8,000 to 9,000 calls per day.

The Red Cross quickly set up Houston’s George R. Brown Convention Center and other venues as shelters. The center, which was also used as a shelter for Katrina refugees from New Orleans in 2005, can accommodate roughly 5,000 people. By Monday morning, it was already half full.

The Army Corps of Engineers started the releases from the Addicks and Barker reservoirs ahead of schedule early Monday because water levels were increasing at a rate of more than 6 inches (15 centimeters) per hour, Corps spokesman Jay Townsend said.

People living near the reservoirs were warned Sunday about the risk that the releases could cause additional street flooding that could spill into homes.

The Army Corps said it a statement that it was confident that the structures would “continue to perform as they were designed to do.” A $75 million fix to the two dams’ floodgates is slated for completion in 2019.

In the Cypress Forest Estates neighborhood in northern Harris County, people called for help from inside homes as water from a nearby creek climbed to the same level as their eaves. A steady procession of rescue boats floated into the area.

One man, Joe Garcia, carried his German shepherd in the chest-deep water before being picked up by a boat. Garcia said he floated out a tub of his belongings, then went back in for the dog.

Up to 20 more inches (51 centimeters) of rain could fall in the coming days, on top of the more than 30 inches (76 centimeters) some places have already seen, National Weather Service Director Louis Uccellini said Monday.

That means the flooding will get worse in the days ahead and that the floodwaters will be slow to recede once Harvey finally moves on, the weather service said.

The amount of water in Houston was so unprecedented that meteorologists had to update the color charts on the weather service’s official rainfall maps.

Bands of heavy rain extended to southwest Louisiana, and Gov. John Bel Edwards said flooding could pose a “dangerous situation.”

Images of the devastation in Houston stirred up painful memories for many Hurricane Katrina survivors in Louisiana.

“It really evoked a lot of emotions and heartbreak for the people who are going through that now in Houston,” Ray Gratia said as he picked up sandbags for his New Orleans home, which flooded during the 2005 hurricane.

In Washington, President Donald Trump’s administration assured Congress that the $3 billion balance in FEMA’s disaster fund was enough to handle immediate needs, such as debris removal and temporary shelter for thousands of displaced residents. When lawmakers return next week, a multibillion-dollar aid package is likely to be added to their already packed agenda.

Trump planned to visit Texas on Tuesday, accompanied by first lady Melania Trump.

Harvey was the fiercest hurricane to hit the U.S. in 13 years and the strongest to strike Texas since 1961’s Hurricane Carla, the most powerful Texas hurricane on record.