Houston's mayor insists that America's fourth-largest city is “open for business,” but with areas under water, people not yet in their homes, and billions in damage to repair, major disasters that Hurricane Harvey created are by no means resolved.

Mayor Sylvester Turner said much of the city was hoping to get back on track after Labour Day.

“Anyone who was planning on a conference or a convention or a sporting event or a concert coming to this city, you can still come,” he told CBS. “We can do multiple things at the same time.”

One worry, of further explosions at a damaged chemical plant, lessened after officials carried out a controlled burn on Sunday evening of highly unstable compounds at the Arkema plant in Crosby. Three trailers had previously caught fire after Harvey's floodwaters knocked out generators.

Authorities said they would keep monitoring the air, and people living within a mile and a half of the site outside Houston are still evacuated. But floodwaters also have inundated at least five toxic waste Superfund sites near Houston and some may be damaged, though Environmental Protection Agency (EPA) officials have yet to assess the full extent of what occurred.

Texas Governor Greg Abbott told CNN the EPA is “working on some of them already,” but “they have restraints on their ability to check out some of them just simply because of the water.”

Turner said Houston's drinking water hadn't been affected by the storm, but told CBS, “We would hope that the EPA would be on the ground now to take a look at those Superfund sites, to make sure that contamination is contained and limited.”

Other issues across the region: too much water still in houses, no water to drink.

Utility crews went door-to-door on Sunday shutting off power and warning those still in some waterlogged homes in western parts of the city that more flooding was possible — not from rain, but from releases of water from overtaxed reservoirs. Thousands of Houston dwellings were under mandatory evacuation orders, though about 300 people were thought to be refusing to leave.

People briefly returned on Sunday to some homes in the area, which included brick two-storey and ranch homes bordering Buffalo Bayou, to try to salvage valuables.

More than a week since the storm hit, the 4 feet of water in her parents' home had receded just a foot, said Karen Mace. She was trying to retrieve family photos from the one-storey ranch her parents built and have lived in for 56 years, which backs up to Buffalo Bayou.

“It came up fast. They had to get out by canoe,” Mace said, adding they thought the home would have to be demolished.

Harvey slammed into Texas on 25 August as a Category 4 hurricane, but brought the worst flooding to Houston and other areas as a tropical storm. The rain totaled nearly 52 inches (1.3 metres) in some spots, and the storm is blamed for at least 44 deaths.

In other storm-ravaged neighbourhoods, people worried about thefts.

Police in the southwest Bellaire neighbourhood received reports of scavengers picking through water-damaged possessions and urged those cleaning up to keep anything left outside to dry closer to their homes and separate from what was considered a total loss. In the suburb of Dickinson, one homeowner used orange spray paint on a sheet of dirty plywood to warn: “Looters Will B Shot.”

The aftermath of Hurricane Harvey Show all 19 1 /19 The aftermath of Hurricane Harvey The aftermath of Hurricane Harvey A tattered U.S. flag damaged in Hurricane Harvey, flies in Conroe, Texas Reuters The aftermath of Hurricane Harvey Lisa Rehr holds her four-year old son Maximus, after they lost their home to Hurricane Harvey, as they await to be evacuated with their belongings from Rockport, Texas Reuters The aftermath of Hurricane Harvey People line up for food as others rest at the George R. Brown Convention Center AP Photo/LM Otero The aftermath of Hurricane Harvey Volunteers with The American Red Cross register evacuees at the George R. Brown Convention Center Reuters/Nick Oxford The aftermath of Hurricane Harvey Soldiers with the Texas Army National Guard help the residents of Cyprus Creek Reuters The aftermath of Hurricane Harvey Residents wade through floodwater Reuters/Nick Oxford The aftermath of Hurricane Harvey Residents walk along the flooded roadway of Texas 249 as they evacuate their adjacent neighborhoods EPA The aftermath of Hurricane Harvey A man floats past a truck submerged on a freeway flooded by Tropical Storm Harvey on Sunday AP The aftermath of Hurricane Harvey People are rescued by airboat as they evacuate from flood waters from Hurricane Harvey in Dickinson, Texas Reuters The aftermath of Hurricane Harvey James Archiable carries his bike through the flooded intersection at Taylor and Usenet near downtown Houston, Texas EPA The aftermath of Hurricane Harvey A massive sinkhole opened up on a motorway in Rosenburg, a city 25 miles southwest of Houston, Texas Rosenberg Police The aftermath of Hurricane Harvey People are rescued from flood waters from Hurricane Harvey in an armored police mine-resistant ambush protected vehicle in Dickinson, Texas Reuters The aftermath of Hurricane Harvey People are rescued from flood waters from Hurricane Harvey on a boat in Dickinson, Texas Reuters The aftermath of Hurricane Harvey Evacuees are airlifted in a US Coast Guard helicopter after flooding due to Hurricane Harvey inundated neighborhoods in Houston, Texas Reuters The aftermath of Hurricane Harvey Evacuees leave a US Coast Guard helicopter after being rescued from flooding due to Hurricane Harvey in Houston, Texas Reuters The aftermath of Hurricane Harvey Residents look on at a submerged motorway during a break in the rain in Houston, Texas EPA The aftermath of Hurricane Harvey People photograph the submerged motorway interchange EPA The aftermath of Hurricane Harvey Debris lies on the ground after a building was destroyed by Hurricane Harvey in Aransas Pass, Texas AP The aftermath of Hurricane Harvey Dominic Dominguez searches for his boat in a boat storage facility that was heavily damaged by Hurricane Harvey near Rockport, Texas EPA

Meanwhile, repairs continued on the water treatment plant in Beaumont, about 85 miles from Houston, which failed after the swollen Neches River inundated the main intake system and backup pumps halted. And outside the town of Liberty, about 45 miles from Houston, dozens of people were still cut off by the swollen Trinity River. A Texas National Guard helicopter landed at the local fire department with pallets of drinking water.