HOUSTON — A series of explosions at a flood-damaged chemical plant outside Houston on Thursday drew sharp focus on hazards to public health and safety from the city’s vast petrochemical complex as the region begins a painstaking recovery from Hurricane Harvey.
The blasts at the plant, owned by the French chemical company Arkema, came after its main electrical system and backups failed, cutting off refrigeration systems that kept volatile chemicals stable. While nearby residents had been evacuated, 15 public safety officers were treated at a hospital after inhaling smoke from chemical fires that followed the explosions.
The Arkema plant has been identified as one of the most hazardous in the state. Its failure followed releases of contaminants from several other area petrochemical plants and systemic breakdowns of water and sewer systems in Houston and elsewhere in the storm-struck region.
The explosions — more are expected, the company said — will bring fresh scrutiny on whether these plants are adequately regulated and monitored by state and federal safety officials.
The chemical plant accident came as devastation from Harvey, now a tropical depression moving into the Mississippi Valley, continued to spread across the region. The known death toll from the storm and flooding remained at 38, the authorities said.
Record-breaking floods swept through Beaumont, Tex., 100 miles east of Houston, damaging the water system and leaving the city’s 120,000 residents without clean water.
Faced with that prospect, one hospital, Baptist Beaumont, began to transport most of its 193 patients to other hospitals outside the city. “We’re doing this before we’re in crisis mode,” a spokeswoman said.
Beaumont city officials said they would not be able to assess the damage to the water system until floodwaters began to recede, and that efforts were being made to distribute bottled water. But Harvey dropped nearly four feet of rain in the area, and most roads into the city remained impassable.
“Right now, Beaumont’s basically on an island,” a police spokeswoman said.
While many areas continued to face the threat of rising waters, and rescues from flooded homes were continuing, many Houston residents began to return home for the first time in nearly a week to assess the damage.
Vice President Mike Pence and several cabinet officials arrived in Corpus Christi, Tex., around midday on Thursday before heading to nearby Rockport to survey the devastation left by the storm, speak with victims and survey the cleanup effort.
“The American people are with you,” Mr. Pence told a crowd gathered outside a Rockport church.
Tom Bossert, the official leading the White House’s response to the disaster, estimated that 100,000 homes in Texas and Louisiana had been damaged or destroyed, and said that President Trump would soon seek billions in aid.
Mr. Bossert said that rescuers would provide aid to the estimated 500,000 undocumented immigrants in the Houston area, and that federal officials would not round up those whose only offense was entering the country illegally. But undocumented immigrants would likely not be eligible for long-term aid, he said, including subsidies to replace damaged housing.
Last week, with the forecast of an approaching hurricane, executives at Arkema decided to shut down the plant in Crosby, about 30 miles northeast of Houston, as a precaution. Most of the 60 workers were sent home on Friday; only a “ride-out” crew of 11 stayed behind.
The flooding brought on by the weekend’s torrential rainfall knocked out electrical power to the plant on Sunday. Backup generators were inundated as well.
The plant produces chemicals that need to be kept cold to avoid becoming unstable and explosive. With refrigeration equipment not functioning, cold-storage warehouses that held the chemicals began to warm.
Fearing that the chemicals might explode, the workers as a last resort transferred them to nine refrigerated trailers on the property. All but one of the refrigeration units on those trailers eventually failed, the company said.
With no way to prevent explosions, the workers abandoned the site late Tuesday.
Company officials said they had been prepared for a major storm, but nothing of the magnitude that hit.
“Certainly we didn’t anticipate having six feet of water in our plant,” Richard Rennard, an Arkema executive, said at a news conference Thursday. “And this is really the issue that led to the incident we are experiencing now.”
M. Sam Mannan, a professor of chemical engineering at Texas A&M University and the author of a study on Texas chemical plants that listed the Arkema plant as one of the most hazardous in the state, said he could understand why company officials did not foresee such extreme flooding.
Still, the dangers of the chemicals they produce should have prompted them to plan for the worst, he said.
“They knew they were dealing with an unstable chemical that they need to keep refrigerated,” he said. “So the question becomes, could they have done something else?”