The remains found on the side of the railroad tracks in Manassas Park that led to an investigation which bogged down the commute for hundreds of Virginia Railway Express passengers late Wednesday are not human, the Virginia Medical Examiner’s office has verified.

Manassas Park police said in a statement that detectives and the medical examiner’s office were on the scene Wednesday to investigate the remains, and have determined that they are not human, although officials did not immediately say what they are and how they got there.

Police say a “concerned citizen” found the remains and reported it to police.

The investigation delayed about 2,000 VRE passengers and some from Amtrak, making for a lengthy, difficult commute.

VRE spokesman Mark Roeber said the agency used its partnerships with bus lines in Fairfax, Alexandria and Prince William to get passengers home.

He said that while most were understanding of the wait, others expressed displeasure. But he said that it took awhile for buses to finish routes and officials to reroute drivers in rush-hour traffic.

“In terms of rapid response, that is as rapid as you can go at the time that it is occurring,” Roeber said. “It’s not like we have buses just sitting around waiting for us to have an incident.”

This post has been updated since it was first published.