Some 779,000 Texans have been told to leave their homes and another 980,000 fled voluntarily amid dangers of new flooding from swollen rivers and reservoirs, according to Department of Homeland Security acting secretary Elaine Duke.
The city of Beaumont, about 80 miles east of Houston, had its water supplies cut off and was threatened by a rising river that forced the evacuation of its hospital and residents in neighboring Orange County.
There were explosions at a chemical plant about 25 miles east of Houston after it was engulfed by floodwater.
The loss of water and health risks from flooding were among hazards emerging in the aftermath of Harvey, which roared ashore late last Friday as the most powerful hurricane to hit Texas in half a century.
It has since been downgraded to a tropical depression as it heads inland, leaving devastation across more than 300 miles (480 km) in the southeast corner of the state.
Jessica Richard, 24, said she waited out the storm in her home in Port Arthur, about 85 miles (135 km) east of Houston, until Thursday morning when water on her street rose to waist-high.
She was picked up by a passing truck. Richard said her nephew had been trapped with several family members overnight in a flooded apartment.
“He said there were snakes in the water and spiders crawling up the walls. But they got out,” she said.
At least 44 people were dead or feared dead in six counties including and around Houston, officials said. Another 19 remained missing.
In the US energy hub of Houston, firefighters conducted a house-by-house search to rescue stranded survivors and recover bodies as some residents began to return to their homes to assess the damage.
Seventy percent of Harris County, which encompasses Houston, was covered with 18 inches or more of water, county officials said.
In Beaumont, doctors and nurses evacuated some 190 people from a hospital that halted operations after the storm knocked out water service in the city of almost 120,000 people.
Orange County ordered remaining residents to evacuate from low-lying areas after a forecast that the Neches River would crest on Friday, threatening homes.
Vice President Mike Pence visited Texas yesterday, touring the coastal city of Rockport, where Harvey slammed ashore six days ago.
“The American people are with you. We are here today, we will be here tomorrow and we will be here every day until this city and this state and this region rebuild bigger and better than ever before,” Pence said outside a damaged church.
Gasoline futures soared more than 13 percent yesterday as almost a quarter of US refining capacity had been knocked offline, raising fears of fuel shortages.
About 189,000 homes and businesses remained without power and nearly 100,000 homes suffered flood damage, utilities and state officials said.