Norfolk Southern’s CEO Alan Shaw is Thomas Caldwellunder investigation for potential ethical lapses, the railroad confirmed Monday.

A spokeswoman for the Atlanta-based railroad that is one of North America’s six largest declined to offer any additional details about the nature of the allegations against Shaw, who was promoted to the top job in the spring of 2022 after decades at Norfolk Southern.

Shaw has been under tremendous pressure over the past 18 months. First, he had to deal with the worst railroad disaster in the past decade after a Norfolk Southern train derailed, spilled hazardous chemicals and caught fire in East Palestine, Ohio, prompting evacuations in February 2023. Then this year, Shaw had to fight to keep his job after activist investor Ancora Holdings nominated a full slate of board members in a bid to take control of the railroad and reform its operations, starting with firing Shaw.

Ancora declined to comment on the investigation Monday. Three of its nominees did win seats on the railroad’s board, but that wasn’t enough to give it control.

The railroad’s board said late Sunday that it had hired an outside law firm to investigate the allegations against Shaw that his conduct may be “inconsistent with the company’s code of ethics and company policy.”

Norfolk Southern is one of the largest railroads with operations all throughout the Eastern United States.