LOS ANGELES, Feb. 1 (UPI) -- William Peterson, an original star of the U.S. TV series "CSI: Crime Scene Investigation," will appear in an upcoming episode, Entertainment Weekly said.

The magazine said Monday it has learned exclusively that Peterson, who played forensic entomologist Gil Grissom on the hit crime drama, has already filmed a cameo but it was not clear when the episode will air.

When Peterson left the series in 2009, he and the show's other producers indicated Grissom would show up in the series from time to time.

"I think there's a way for the audience to remember him, like losing a great co-worker they've known for years," Petersen told EW at the time. "He didn't die in a plane crash, he didn't get a brain tumor. He's out there."