Authorities are trying to recover the bodies of a pilot and co-pilot killed when a small cargo jet crashed into a river in an Illinois forest preserve.

SLIDESHOW: Small Jet Crashes Outside Chicago

Cook County Forest Preserve Police spokesman Steve Mayberry says officials are working Wednesday to remove the crumpled plane wreckage from the Des Plaines River in unincorporated Glenview. Emergency crews, including divers, located the two bodies Tuesday evening after the crash, but Mayberry says the bodies have yet to be recovered.

The Learjet Model 35 crashed shortly after it was cleared to land at Chicago Executive Airport in suburban Wheeling. It had departed Oakland County International Airport in Waterford, Mich., outside Detroit.

The Federal Aviation Administration says the cause of the crash isn't immediately clear.

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