FOREST PARK, Ill. -- FOREST PARK, Ill. (AP) — The federal investigation into the crash of an unmanned Chicago commuter train is continuing, but the government shutdown has meant there's nobody around to talk about it.

Tim DePaepe of the National Transportation Safety Board said Monday that once the agency's investigators are on a scene they are considered "essential" and would not be furloughed as part of the government shutdown that began at midnight.

But callers to the NTSB public affairs office Tuesday were told by a recording that "due to lapse in funding" the office is closed.

Investigators are trying to determine how the out-of-service train rolled about a half mile before crashing into an occupied train. As many as 48 people had minor injuries.

The accident happened in Forest Park on the Chicago Transit Authority's blue line.

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  • Authorities inspect the wreckage of two Chicago Transit Authority trains that crashed Monday, Sept. 30, 2013, in Forest Park, Ill. The crash happened when a westbound train stopped at the CTA Blue Line Harlem station, and was struck by an eastbound train on the same track. The CTA is investigating the cause of the crash, including why the trains were on the same track. A CTA official said 33 people suffered non-life threatening injuries. (AP Photo/M. Spencer Green)

  • Authorities inspect the wreckage of two Chicago Transit Authority trains that crashed Monday, Sept. 30, 2013, in Forest Park, Ill. The crash happened when a westbound train stopped at the CTA Blue Line Harlem station, and was struck by an eastbound train on the same track. The CTA is investigating the cause of the crash, including why the trains were on the same track. A CTA official said 33 people suffered non-life threatening injuries.(AP Photo/M. Spencer Green)

  • This image from video provided by NBC Chicago shows the aftermath of a crash involving two Chicago Transit Authority trains on the Blue Line during rush hour Monday, Sept. 30, 2013, in Forest Park, Ill. Several ambulances have been sent to the scene. (AP Photo/Courtesy of NBC Chicago)

  • This image from video provided by NBC Chicago shows emergency personnel at the scene of a crash involving two Chicago Transit Authority trains on the Blue Line during rush hour Monday, Sept. 30, 2013, in Forest Park, Ill. Several ambulances have been sent to the scene. (AP Photo/Courtesy of NBC Chicago)

  • This image from video provided by NBC Chicago shows emergency personnel at the scene where two Chicago Transit Authority trains on the Blue Line collided during rush hour Monday, Sept. 30, 2013, in Forest Park, Ill. Several ambulances have been sent to the scene. (AP Photo/Courtesy of NBC Chicago)

  • Emergency personnel work at the scene where two Chicago Transit Authority trains collided during rush hour Monday, Sept. 30, 2013, in Forest Park, Ill. About four dozen people were injured in the accident, most complaining of back and neck pain. None were serious. Firefighters from up to a dozen local fire departments responded to the crash. (AP Photo/Don Babwin)