Police are hunting for a convicted murderer after he was mistakenly released from custody in Chicago, where he was sent to face a drug charge while serving a 60-year prison sentence in Indiana.

Indiana Department of Corrections officials say Steven L. Robbins, 44, was sent to Cook County Circuit Court on Tuesday to face a drug charge. The charge was dropped, "but for reasons yet unknown, the offender was released by Illinois authorities without being held for return," the department said in a news release.

The Indiana Department of Corrections had submitted paperwork telling Illinois officials that Robbins was supposed to be returned to Indiana, spokesman Douglas Garrison said Friday.

"It's quite clear that all of the paperwork from IDOC was in order, so that they would have known that he was supposed to be returned to us," Garrison said.

The Cook County Sheriff's Office said it was investigating how Robbins was released Wednesday evening.

Robbins, a Gary, Ind., native, was serving the decades-long sentence for murder and weapons convictions out of Marion County in Indiana. He started serving the sentence in October 2004 and his earliest projected release date was more than 16 years from now, on June 29, 2029.

Both Illinois and Indiana have issued arrest warrants for Robbins. Officials in both states are asking for the public's help to apprehend him.

Information about Robbins' murder case wasn't immediately available Thursday evening.