London, Sep 22 - Hollywood movie bosses are reportedly planning a second Sherlock Holmes film even before the first instalment has hit the big screen.

The film's trailer has received mixed reviews by critics but movie chiefs are rounding up writers to draft a script for a follow-up to the Arthur Conan Doyle tale, according to the Hollywood Reporter.

Robert Downey Jr. stars as the legendary detective while British actor Jude Law is taking on the role of Dr. Watson in the Guy Ritchie movie, which is set for a December release.

Law has already expressed his desire for the film to be turned into a movie franchise, so the cast can work on more detective stories.

'We would love that the audience falls in love with it (the movie) as much as we have, as then we can (make) a whole bunch more,' he had said.

Downey Jr. is also keen to star in a follow-up.

'We definitely agreed to renegotiate for a part two. We feel really strongly about that. We might shoot the next one abroad,' said Downey Jr.