Under Biden’s order, teams from the Centers for Disease Control and Prevention, Environmental Protection Agency and Federal Emergency Management Agency will visit homes beginning Saturday. Workers will ask how residents are doing, see what they need and connect them with appropriate resources from government and nonprofit organizations, the White House said.

The “walk teams” are modeled on similar teams following hurricanes and other natural disasters.

Biden directed employees to get to as many homes as possible by Monday. Officials said the immediate goal was to visit at least 400. The president said he currently has no plans to personally visit Ohio.

Meanwhile, the controversy spread far beyond the little Ohio town. Officials in Texas and Michigan expressed concern about contaminated wastewater and soil being transported to their states for disposal.

Biden’s order came as House Republicans opened an investigation into the Feb. 3 derailment, blaming Transportation Secretary Pete Buttigieg for what they contend was a delayed response to the fiery wreck. The focus on DOT came even though the EPA took charge of the federal response this week and ordered Norfolk Southern railway to pay for the cleanup and chemical release.

Rep. James Comer, chairman of the House Oversight Committee, became the latest lawmaker to jump into what has become a political proxy war as each party lays into the other after the derailment and chemical leak that led to evacuation of the small Ohio community.

“Despite the U.S. Department of Transportation’s responsibility to ensure safe and reliable transport in the United States, you ignored the catastrophe for over a week,” the Kentucky Republican said in a letter to Buttigieg. “The American people deserve answers as to what caused the derailment, and DOT needs to provide an explanation for its leadership’s apathy in the face of this emergency.”

A preliminary report released Thursday by the National Transportation Safety Board stated that the crew operating the Norfolk Southern freight train didn’t get much warning before dozens of cars went off the tracks and there is no indication that crew members did anything wrong.

Republicans are framing the incident as a moral failing at the hands of the Biden administration, noting Buttigieg’s failure to visit the site until nearly three weeks after the wreck. Democrats point to rollbacks former President Donald Trump made during his term that weakened rail and environmental regulations. EPA Administrator Michael Regan visited the site last week and again on Tuesday.

Biden on Friday rejected the notion that his administration hasn’t been present in providing assistance.

“We were there two hours after the train went down. Two hours,” Biden said at the White House. “I’ve spoken with every single major figure in both Pennsylvania and in Ohio. And so the idea that we’re not engaged is simply not there.”

A timeline given out by the White House Friday said DOT provided “initial incident notification” to members of the Ohio congressional delegation and relevant committees on Saturday, Feb. 4, less than a day after the derailment.

That same day, EPA deployed real-time air monitoring instruments in 12 locations surrounding the wreck site and in the neighboring community, the White House said.

White House staffers reached out to Ohio Gov. Mike DeWine’s office on Sunday, Feb. 5 to offer additional federal assistance, the White House said in its most detailed account of the initial federal response to the wreck, which has led to round-the-clock news stories.

The Oversight letter requests documents and communications concerning when DOT leaders learned of the derailment and whether they received any guidance about what the public response should be, as well any recent changes to agency train maintenance and procedures.

A day earlier, Buttigieg made his first visit to the crash site and hit back at Trump, who had visited the day before and criticized the federal response.

Buttigieg told reporters that if the former president — and current Republican presidential candidate — felt strongly about increased rail safety efforts, “one thing he could do is express support for reversing the deregulation that happened on his watch.”

On Friday, Buttigieg chided Comer for referring in his letter to “DOT’s National Transportation Safety Board,” saying he was “alarmed to learn” the committee chairman “thinks that the NTSB is part of our Department. NTSB is independent (and with good reason). Still, of course, we will fully review this and respond appropriately.”

White House press secretary Karine Jean-Pierre excoriated “political stunts that we’re seeing from the other side.”

Norfolk Southern said the NTSB report showed the train’s heat detectors worked as intended and the crew operated “within the company’s rules.” Nevertheless, the company said it would “need to learn as much as we can from this event” and “develop practices and invest in technologies that could help prevent an incident like this in the future.”

The freight cars that derailed on the East Palestine outskirts, near the Pennsylvania state line, included 11 carrying hazardous materials. Residents evacuated as fears grew about a potential explosion of smoldering wreckage.

Worried about an uncontrolled blast, officials released and burned toxic vinyl chloride from five rail cars, sending flames and black smoke into the sky. That left people questioning potential health effects, though authorities maintained they were doing their best to protect people.

“This incident is an environmental and public health emergency that now threatens Americans across state lines,” Comer and nearly two dozen Republicans said in their letter to Buttigieg.

Environmental controversy extended more than 1,000 miles to Texas, where a Harris County official raised questions about the transportation and disposal of toxic wastewater that was moved to a Houston suburb from the site of the Ohio derailment.

County Judge Lina Hidalgo said a half-million gallons of wastewater from the site had been delivered to Deer Park, Texas, with 1.5 million more gallons set to arrive. The wastewater has been delivered to Texas Molecular, which injects hazardous waste into the ground for disposal.

Contaminated soil from the site will be moved by truck to a disposal site near Ann Arbor, Michigan, Ohio Gov. DeWine’s office said, prompting a complaint from Rep. Debbie Dingell, D-Mich.

“We were not given a heads up on this reported action,” said Dingell, who represents the area. She said she would contact DeWine’s office as well as federal and Ohio officials and Norfolk Southern “to understand what is being shipped … and how we ensure the safety of all Michigan residents.”

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Associated Press writer Zeke Miller contributed to this story.