Red Bull's engine supplier Renault has confirmed former Mercedes technical director Bob Bell is now working with the French manufacturer as a consultant.
Bell, who had previously worked at the Renault F1 tam as a technical director, left Mercedes at the end of last year.
The Briton joined Mercedes from Renault in 2011, having been with the French marque since 2001.
He was the team's technical director during the highly successful 2005 and 2006 seasons and was named team principal after Flavio Briatore left following the 2009 Singapore Grand Prix scandal.
A Renault spokesperson confirmed to Motorsport.com: "Bob is an external consultant on a variety of matters."
Renault is evaluating plans to expand its F1 operation for a better marketing return, perhaps with a takeover of one of the current teams.
Toro Rosso is understood to be favourite, although Sauber and Force India are also being considered.
Bell has joined Renault's managing director Cyril Abiteboul in visiting factories as part of the evaluation process as the French car manufacturer considers its long-term options.
No decision has yet been made about what it will do.