(NEW YORK) -- A series of rail cars that Norfolk Southern recently put into service have been discovered to have defective, loose wheels.
These defective wheel sets were involved in one of the several recent derailments Norfolk Southern has had, including the most recent one in Springfield, Ohio.
Norfolk Southern first identified the defective wheels during the cleanup at Springfield -- the day after the derailment -- on March 5.
Norfolk Southern determined that this "specific model and series of railcars had loose wheels, which could cause a derailment," the company confirmed in a statement to ABC. "The investigative team identified these wheels as coming from a series of recently acquired cars from a specific manufacturer."
The catch comes as the company already faces intense scrutiny for its string of high-profile derailments and other incidents.
The company said they "immediately notified" the NTSB and the Federal Railroad Administration (FRA) once they found the issue "and began inspecting other cars from this series on our network" which led them to discover additional cases of "unusual wheel movement."
Norfolk Southern issued orders to take the cars with these wheels out of service until the wheelsets could be replaced, and are removing the model and series from service for inspection. The company also says they notified the manufacturer and "worked urgently" to inform the rest of the railroad industry since these wheelsets are not proprietary to Norfolk Southern.
"Norfolk Southern will continue to investigate this matter and take appropriate action," the company said in their statement.
The Association of American Railroads has now issued guidance to pull relevant cars off the tracks and inspect them -- and to immediately replace suspect wheelsets with new ones.
"A member railroad has experienced three loose wheels" in cars that are of "new builds," their advisory, reviewed by ABC, said.
An AAR spokesperson confirms to ABC that the "member railroad" they refer to is indeed Norfolk Southern.
The spokesperson called this an "uncommon defect" as well as one that "demanded urgent action."
"This is a voluntary, proactive step aimed at ensuring equipment health and integrity," the spokesperson said.
AAR's advisory says to "inspect and remove from service" the wheelsets mounted by National Steel Car between August 2022 and March 2023.
"These wheelsets are at an increased risk of an out of gage derailment," AAR's advisory reads. "All cars included in this advisory must be inspected for the wheelsets in question and reported as outlined below. Any cars, loaded or empty, found so equipped must have the NSC-T mounted wheel sets removed immediately as directed below. If available, replace suspect wheel sets with new wheel sets."
"Yesterday, Norfolk Southern identified loose wheels on a series of cars that presents an increased risk of an out of gage 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," the spokesperson said.
ABC News has reached out to National Steel Car for comment.