HOUSTON — New proof of the devastation wrought by monster storm Harvey emerged on Wednesday as the bodies of six family members were plucked from receding waters in Texas and flooding triggered fears of a chemical explosion near Houston.

While clouds parted in America’s fourth-largest city, bringing a welcome respite after the storm turned roads into rivers, rural areas of Texas were drenched as Harvey headed eastwards with the city of Port Arthur especially hard hit.

Authorities in neighboring Louisiana scrambled to safeguard their state from the impact of Harvey, whose onslaught evoked painful memories of Hurricane Katrina’s deadly strike 12 years ago – but New Orleans escaped with minimal rain.

Taking advantage of a lull in the rainfall in Houston, rescuers recovered the bodies of six family members from a van which was swept away by the floods over the weekend.

Manuel and Belia Saldivar and four of their great-grandchildren ranging from six to 16 years in age went missing on Sunday.

"Our worst fears have been realised," Harris County Sheriff Ed Gonzalez told a press conference, confirming all six bodies had been found inside the van.

So far, officials believe at least 33 people to have been killed in the storm, and there is little doubt the toll will rise further – although many of those unaccounted for may simply have no access to phones or power.

"To those Americans who have lost loved ones, all of America is grieving with you, and our hearts are joined with yours forever," President Donald Trump said in a speech, a day after viewing some of the damage for himself on a trip to Texas.

More than 30,000 people have found refuge in shelters across the Lone Star State, from the giant Houston convention center to small churches, according to the head of the Federal Emergency Management Agency (FEMA), Brock Long.

In Houston, where Mayor Sylvester Turner issued an nighttime curfew to aid search efforts and thwart potential looting, the two major airports reopened on a limited basis, signalling a slow return to normality.

Turner told a news conference Wednesday night that trash pickup and metro service will resume in some areas where flood waters have receded.

"It’s my hope that despite how massive this storm has been, that the city of Houston will quickly move to get back to where we were and then beyond that," Turner said.

The National Hurricane Center downgraded Harvey to a tropical depression Wednesday night, but warned that life-threatening flood conditions remain in southeast Texas and southwest Louisiana.

But at least a quarter of Harris County, which includes Houston, is still under water – and the operators of an organic peroxides plant outside the city warned they were bracing for the risk of an explosion after flooding caused them to lose all power.

"Right now, we have an unprecedented six feet of water at the plant," Rich Rowe, president and chief executive of plant operator Arkema Inc, said in a statement.

"We have lost critical refrigeration of the materials on site that could now explode and cause a subsequent intense fire," he said. "The high water and lack of power leave us with no way to prevent it."

As a precaution, officials had already ordered the evacuation of an area within three kilometres of the plant in Crosby, northeast of Houston, and Rowe said the facility itself had been evacuated for employees’ safety.

City underwater

Even as Houston got a first glimpse of life-after-Harvey, the city of Port Arthur was pummeled by torrential rains – making it almost impossible to reach despite the best efforts of volunteer rescuers.

"Our whole city is underwater right now," Port Arthur’s mayor, Derrick Freeman, posted on Facebook early Wednesday – assuring stranded residents that help was on the way.

Justin Coleman was part of a crew of three jeeps and three boats that drove overnight from Fort Worth trying to reach Port Arthur, but were forced to turn around on their first attempt.

"We’re on the radio with them right now and every 30 seconds there’s another person rescued," the 33-year-old said during a pit stop at a gas station in the nearby town of Winnie.

"There’s a lot of babies and elderly that are stuck in their homes right now. They said it’s getting up to their chests," said Coleman, who runs a construction company.

So far, parts of Texas have seen more than 1.27 metres of rain, while in Louisiana, the top total 18 inches so far was increasing.

Dodged a bullet

Harvey first slammed onshore as a Category Four hurricane last Friday night before unloading on Texas.

Although now downgraded to a tropical storm, Harvey made its second landfall just west of the Louisiana town of Cameron early Wednesday, packing maximum sustained winds nearing 45 miles per hour.

Forecasters are predicting another five to 10 inches of rain in the region, with the downpour finally expected to stop today.

For now, southwestern Louisiana is taking the hardest hit, with a levee being breached in the town of Gueydan.

While New Orleans appeared to have dodged a bullet, the arrival of Harvey nevertheless served as a somber reminder, coming just one day after the 12-year anniversary of Katrina, which ravaged the vulnerable city famous for its jazz music and cuisine.

"I began to pray for the people in Texas after having gone through that same experience myself as a Katrina survivor," said Crystal Harris, who works for a bank which was taking donations for storm victims.

Lessons learned

In Texas, the damage wrought is staggering – Enki Research put its "best estimate" at between $48 billion and $75 billion.

At least one bridge had crumbled, one levee had breached and dams were at risk, while Harvey sparked the closure of several major refineries across what is a major hub of America’s oil industry.

More than 4,500 people and 1,000 pets have been rescued from the storm zone by the Coast Guard, which expected to rescue an additional 1,000 people on Wednesday in the Port Arthur area alone.

The Coast Guard has deployed about 50 aircraft and two dozen boats, but the overall rescue effort, involving other military branches and state police, easily tops more than 100 aircraft.

"We are certainly bringing lessons learned from Katrina," Admiral Paul Thomas, who oversees Coast Guard operations in 26 states, told reporters in New Orleans – noting that several members of his team are Louisiana natives who are veterans of the 2005 disaster. — AFP