The agency is pursuing the dismissals after determining the controllers left early before the March crash, according to Reuters. The cause of the collision remains under investigation.

The Federal Aviation Administration is moving to fire two air traffic controllers who left work early before a fatal March collision between an Air Canada Express aircraft and an airport fire truck at New York’s LaGuardia Airport, Reuters reported, citing a source familiar with the matter.

The crash killed the plane’s pilot and co-pilot. The collision occurred after the aircraft landed as the fire truck was crossing airport pavement to respond elsewhere, according to CNN’s reporting.

The FAA said it is committed to holding employees accountable and would not compromise the safety or efficiency of the national airspace system. The National Air Traffic Controllers Association said it was discussing the allegations with FAA leadership and declined further comment, Reuters reported.

CNN reported that the controllers are on leave and that the FAA was considering disciplinary action. Reuters reported that the agency is moving to fire them. Neither account establishes that the early departures caused the collision.

The National Transportation Safety Board is continuing its investigation. Its final report, including a probable-cause finding and any contributing factors, has not yet been issued.