EXCLUSIVE: One of television’s biggest drama series franchises is plotting a comeback. I hear CBS is mulling a CSI event series to mark the 20th anniversary of the original series’ October 2000 premiere. The idea is for new installment, from writer Jason Tracey (Elementary), CBS TV Studios and Jerry Bruckheimer TV, to be set in Las Vegas and be a sequel to the mothership CSI: Crime Scene Investigation, sources said. The hope is that the new incarnation would feature original cast members. I hear William Petersen, who headlined CSI for its first nine seasons, and fellow original star Jorja Fox have been approached, but no formal offers have been made.

Monty Brinton/CBS

Sources stress that no deals for the potential CSI revival are done, and that the project is still in early stages and may not come together within a reasonable financial framework. Reps for CBS and CBS TV Studios declined comment.

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CSI: Crime Scene Investigation followed a team of crime-scene investigators for the Las Vegas Police Department as they used physical evidence to solve murders. The original cast included Petersen, Marg Helgenberger (who is currently on another CBS series, All Rise), Fox, George Eads, Gary Dourdan and Paul Guilfoyle. Petersen was succeeded by Laurence Fishburne as CSI’s leading man. He in turn, was followed by Ted Danson.

Created by then-TV novice Anthony Zuiker, CSI: Crime Scene Investigation has been one of CBS’ most important series of the past two decades. Launched to low expectations on October 6, 2000 on the lower-trafficked Friday night, the forensic crime drama was a breakout hit. It became the most watched series on television and established a Thursday stronghold for CBS at a time when NBC was dominating the night.

CSI: Crime Scene Investigation bowed out in 2015 after 15 seasons, having launched a $1 billion franchise for CBS that spanned four series; CSI and spinoffs CSI: Miami, CSI: New York and CSI: Cyber.

In recognition of the mothership series’ legacy, CBS gave it a special sendoff with a two-hour movie finale in September 2015. Not long after that the network, CBS TV Studios and Bruckheimer TV started floating the idea of bringing the procedural franchise back, especially after the last CSI series, Cyber, ended its run in March 2016.

The new project’s writer, Tracey, who would executive produce with JBTV’s Bruckheimer and Jonathan Littman, started his career at JBTV as a staff writer on the company’s the WB series Just Legal. He has worked on several JBTV shows including CBS crime procedural Cold Justice. Tracey recently was on CBS/CBS TV Studios’ Elementary for the drama series’ entire seven-season run, becoming an executive producer at the start of Season 4.

If the new installment comes to fruition, CSI would be the latest broadcast drama to stage a return as a limited series, joining Fox’s 24 (with Live Another Day), Prison Break and The X-Files and NBC’s Heroes.