[above: Toyota F1 team principal Tadashi Yamashina reacts while answering a question on the future of their young F1 drivers, Kamui Kobayashi and Kazuki Nakajima during the press conference announcing the company's withdrawal from F1.]

By Alan Baldwin

LONDON (Reuters) - Formula One's governing body has sought urgent clarification from Toyota about its departure from the sport.

The International Automobile Federation (FIA) said in a statement that Toyota's decision on Wednesday to quit caused concern, as did the announcement by tyre supplier Bridgestone that they would leave at the end of 2010.

"Bridgestone has given almost 18 months' notice of its intentions, thereby allowing the necessary arrangements to be made for the future supply of tyres to the championship," the FIA said.

"Toyota's decision, however, comes just weeks after its F1 team signed the new Concorde Agreement until 2012.

"Urgent clarification is now being sought from the Toyota F1 team as to its legal position in relation to the championship. This will have a direct bearing on the admission of any future 13th entry."

Toyota did not say in a statement issued in Tokyo what they would do with their Cologne-based team, although a source there told Reuters that the plan was simply to close it down.

The former BMW-Sauber team have been named as reserves to take up any slot vacated by one of the 13 teams due to compete in 2010.

However their entry cannot be officially given the green light until Toyota confirm what is happening to their team.

By signing the confidential Concorde Agreement in August, Toyota had committed themselves to Formula One until at least 2012.

The FIA said it had repeatedly warned that "motor sport cannot outpace the world economic crisis" and had acted accordingly to cut costs and allow new, independent teams in.

"The FIA accepted the cost-reduction measures put forward by the teams on the basis that they would ensure a long-term commitment to the championship," it added.

"Toyota's announcement demonstrates the importance of the original cost-reduction measures set out by the FIA.

"The FIA will now work to ensure that Toyota's departure is managed in the best interests of the championship and will continue to encourage the F1 teams to undertake the necessary cost-cutting measures for the good of the sport."