After a series of Norfolk Southern (NS) freight train derailments, the latest accident on Thursday in Alabama, hours before NS CEO Alan Shaw faced lawmakers about the Feb. 3 toxic chemical spill in East Palestine, Ohio, the Association of American Railroads (AAR) issued a rare advisory urging carriers to stop using certain railcars amid concerns about loose wheels.

“Yesterday, Norfolk Southern identified loose wheels on a series of cars that presents an increased risk of an out-of-gauge derailment. Today, AAR, through its committee structure, took expeditious action and has issued an advisory to stop cars with these wheels from use and interchange until those wheel sets can be replaced,” AAR spokeswoman Jessica Kahanek told media outlet Trains.

“This is an uncommon defect to see in a wheelset that demanded urgent action. This is a voluntary, proactive step aimed at ensuring equipment health and integrity,” Kahanek added.

The industry group said railcars designed to carry coiled steel produced by National Steel Car of Hamilton, Ontario, Canada, between August of last year and March should be removed immediately from service.

The advisory comes hours after a Norfolk Southern freight train derailed Thursday in Calhoun County, Alabama. On the same day, NS CEO Alan Shaw testified in a Senate Environment and Public Works Committee hearing about the devastating train derailment in East Palestine.

Reuters noted the National Transportation Safety Board is currently looking into the possible impact of loose wheels on recent train derailments.