William Petersen left the show and was replaced by Laurence Fishburne
CSI star William Petersen, best known for playing Gil Grissom in the hit US drama series, has confirmed a film based on the show will be made.
Petersen, an executive producer on CSI, says he understands fans are "a little trepidatious" about a movie version.
But speaking to the Radio Times, he said: "It's about finding the right story, there has got to be a real reason to do it."
Petersen's character has left the series but may return next year.
"I can understand people are a little trepidatious because of the franchise around the world and how well it's doing," he said.
"Usually people leave it till a series has finished - they did that with The X-Files and Sex And The City. But it's about finding the right story.
"There has got to be a real reason to do it. You don't just do it because you want to make money; you do it because there's a story that can't be told on TV and needs to be told from CSI's perspective and the audience wants it.
"And we can't wait for CSI to end or Grissom will be about 90."
CSI is based on a team of Las Vegas forensic scientists who investigate mysterious and unusual deaths.
In the ninth series Petersen left and was replaced by Matrix star Laurence Fishburne as Dr Raymond Langston.