Jorja Fox also starred in hit medical drama ER

Actress Jorja Fox was fired over a contractual dispute on the day filming was due to begin on a new series.

Co-star George Eads has also reportedly been sacked after a pay row, according to Variety newspaper.

CSI is the US' top-rated show, drawing up to 26 million viewers, and has spawned a number of spin-offs including CSI: Miami and CSI: New York.

Fox, who played Sara Sidle in the drama, was five years in to a seven-year contract with the CBS network.

The 36-year-old previously starred in ER as Dr Maggie Doyle and in a season of The West Wing as Gina Toscano.

Her publicist Danica Smith confirmed the actress had been sacked, but did not go into the reasons for her dismissal.

Fans petition

Ms Smith could not confirm that Eads, also a client, had been fired, although Variety reports he did not turn up for work on the first day of filming.

Eads has previously appeared in ER and romantic comedy Just a Walk in the Park.

Fans of the actors have already begun an internet petition supporting the stars, threatening to stop watching the show if they are not allowed back in the series.

A CBS spokesman said the network had no comment.

The news emerged on the day CSI was nominated for four Emmys, including best drama series.