Senate Commerce, Science, and Transportation Committee hearing in Washington
U.S. Transportation Secretary Pete Buttigieg testifies before a Senate Commerce, Science, and Transportation Committee hearing on President Biden's proposed budget request for the Department of Transportation, on Capitol Hill in Washington, U.S., May 3, 2022. Reuters

U.S. Transportation Secretary Pete Buttigieg toured the wreckage of this month's train derailment and toxic spill in East Palestine, Ohio, on Thursday while federal investigators released their initial report on the Feb. 3 incident.

Little new information emerged from the National Transportation Safety Board's (NTSB) preliminary report about the derailment of the Norfolk Southern train loaded with toxic chemicals.

It said the investigation was focusing on the possibility that an overheated wheelset and bearing on a car triggered the derailment.

Wearing a hardhat and orange safety vest, Buttigieg met with NTSB staff at the scene of the derailment, which sparked the evacuation of thousands of people and ignited health concerns.

The Biden administration had been criticized for not having made a high-level visit sooner. Environmental Protection Agency (EPA) Administrator Michael Regan visited East Palestine earlier this week.

The NTSB was due to hold a news conference at 1 p.m. ET (1800 GMT) to further detail its initial findings.

It also said it was investigating whether pressure relief valves on train cars carrying the toxic chemical vinyl chloride functioned properly following the wreck and subsequent fire.

Experts had said that if those relief valves had functioned properly, authorities may not have needed to drain upward of 1.1 million pounds of vinyl chloride from cars and purposefully set it ablaze, releasing heavy contamination into the environment.

The NTSB said investigators were also looking at how a defect detection system worked and whether the system might have alerted the train engineer to the train's problems earlier.

Norfolk Southern's chief executive apologized on Wednesday at a CNN town hall event that highlighted residents' concerns about soil and ground water contamination.

U.S. President Joe Biden, a Democrat, and his administration have said the company must pay for the damage and clean-up efforts, and the EPA ordered company officials to attend town hall events after executives initially boycotted.

Buttigieg had said he would push major railroads to improve safety and seek bipartisan support in Congress to raise the cap on fines against railroads for violating safety regulations.

Some Republicans have criticized the Biden administration over the incident while some Democrats have pointed to regulations rescinded under former President Donald Trump, a Republican.

Trump, who is campaigning for the 2024 Republican presidential nomination, visited the area on Wednesday.