OMAHA, Neb. (AP) — Union Pacific managers undermined the U.S. government’s efforts to assess safety at the railroad in the wake of several high profile derailments across the industry by coaching employees on how to respond and suggesting they might be disciplined, federal regulators say.

The meddling was so widespread across Union Pacific’s 23-state network that the Federal Railroad Administration had no choice but to suspend its safety assessment of the company, the agency’s chief safety officer, Karl Alexy, told Union Pacific executives in a letter dated last week that labor groups posted online Tuesday.

The company indicated Wednesday that the issue was limited to one department. Its president told FRA in a response letter that Union Pacific“did not intend to influence or impede the assessment in any way.”

The agency launched safety assessments of all major railroads in the U.S. at the urging of congressional leaders after Norfolk Southern’s disastrous February 2023 derailment in eastern Ohio, and the episode with Union Pacific may prompt lawmakers to finally act on stalled railroad safety reforms.