(NewsNation) — A safety program aimed at reducing derailments has gone unused by all the major freight rail companies, according to U.S. Secretary of Transportation Pete Buttigieg.

In a letter to those companies sent Monday, Buttigieg chided Norfolk Southern — the rail company whose train derailed near East Palestine, Ohio — for not participating in the safety program, dubbed the Confidential Close Call Reporting System (C3RS).

The program allows rail employees to report safety hazards — including conditions that could lead to a derailment — without retaliation, Buttigieg wrote. C3RS is a voluntary program sponsored by the Federal Railway Association.

Norfolk Southern isn’t alone, however. While many commuter rail companies including Amtrak take part in the program, the secretary said it has not been used by any major freight rail company.

“By refusing to take this commonsense step, you are sending an undesirable message about your level of commitment to the safety of your workers and the American communities where you operate,” Buttigieg wrote.

C3RS was one of the several actions the transportation department encouraged Norfolk Southern to take immediately following a Feb. 21 communication, Buttigieg wrote in a letter, addressed to Norfolk Southern CEO Alan Shaw.

“I am asking you to join the C3RS program now, even as our Department proceeds to take appropriate steps toward making this program mandatory,” he wrote.

Buttigieg said he sent similar letters to other Class I railroads and requested a reply by the end of the week, so he can present a summary of participating companies.

“Americans will be interested to know whether Norfolk Southern is willing to take this basic step to address safety and help prevent future disasters like the one that occurred in East Palestine, Ohio, and I hope you will welcome this opportunity to demonstrate your intentions,” he wrote.

Leaders of Norfolk Southern or the other major freight rail companies did not immediately issue a response to the secretary’s letter Monday.