The National Transportation Safety Board said Tuesday it is opening a special investigation into Norfolk Southern Railway's safety practices and culture in the wake of a hazardous train derailment in East Palestine, Ohio, and other recent incidents involving the rail operator.
The last time the agency opened such an investigation was in 2014 for Metro-North following several significant accidents.
The U.S. Department of Transportation's Federal Railroad Administration also announced Tuesday that it will conduct a safety assessment of Norfolk Southern's railway safety operations "following multiple safety incidents."
The scrutiny comes after a Norfolk Southern freight train carrying hazardous materials derailed on Feb. 3 near East Palestine, Ohio, sending toxic chemicals into the air, soil and creeks in the area. NTSB Chair Jennifer Homendy called the derailment "100% preventable" and said it was "no accident."
Most recently, a Norfolk Southern train derailed Saturday near Springfield, Ohio. The railroad company told authorities that this incident did not involve hazardous materials. But officials acknowledged Monday that cars on the train that did not derail did have hazardous contents.
MORE: NTSB on East Palestine toxic train derailment: '100% preventable'A Norfolk Southern train conductor was killed in a collision with a dump truck at a rail crossing at the property of steel producer Cleveland-Cliffs, in Cleveland, Ohio, early Tuesday.
"Given the number and significance of recent Norfolk Southern accidents, the NTSB also urges the company to take immediate action today to review and assess its safety practices, with the input of employees and others, and implement necessary changes to improve safety," NTSB said in announcing its investigation.
DOT said information collected in its supplemental assessment will "[provide] a more expansive look at Norfolk Southern's overall safety culture and operations." The probe will review the findings and recommendations of the 2022 Norfolk Southern system audit and revisit FRA's recommendations and the scope of the railroad's responses.
"After a series of derailments and the death of one of its workers, we are initiating this further supplemental safety review of Norfolk Southern, while also calling on Norfolk Southern to act urgently to improve its focus on safety so the company can begin earning back the trust of the public and its employees," U.S. Transportation Secretary Pete Buttigieg said in a press release.
Following the announcement of the NTSB investigation into their safety and culture, Norfolk Southern CEO Alan Shaw told ABC News that "moving forward, we are going to rebuild our safety culture from the ground up."
"We are going to invest more in safety," Shaw said in a statement. "This is not who we are, it is not acceptable, and it will not continue."
Shaw is set to testify before the Senate's Environment and Public Works Committee during a hearing on Thursday amid calls for reform.
A bipartisan group of senators, led by Ohio Democrat Sherrod Brown and Ohio Republican J.D. Vance, introduced legislation last week looking to regulate the railroad industry in the wake of the East Palestine disaster.
"It shouldn't take a rail disaster to get us working together like that. And that's what we're going to be doing," Brown told ABC "This Week" anchor George Stephanopoulos on Sunday.
NTSB's preliminary report into the East Palestine incident found that a wheel bearing appeared to overheat moments before the derailment. A final report with recommendations might not be finished for up to two years, officials said.
Representatives from NTSB were on site Monday investigating the wreck near Springfield.
The cause of the accident is not yet known, Shaw said.
"In some ways, the cause does not matter," he said in his statement Tuesday, adding that he "called together every member of our management team this afternoon to emphasize the urgency of finding new solutions."
The company plans to hold "safety stand-down briefings reaching every employee across our network" on Wednesday, Shaw said.
ABC News' Amanda Maile contributed to this report.