Williams and Caterham's exhaust solutions have not been ruled illegal by the FIA, ESPN understands.

Caterham ran a piece of bodywork over the Coanda exhaust exit on its CT03 at Jerez and was followed by Williams which had two pieces over the exit when it launched the FW35 at the Circuit de Catalunya yesterday. The solutions have been the centre of some interest from the teams, with Williams' Mike Coughlan saying "for me the Caterham one is clearly not allowed, but ours is OK, because if you look at ours it's actually not a single piece it's two pieces".

Williams has revealed that discussions with Charlie Whiting in Barcelona have called in to question whether the bodywork would pass scrutineering and as a result "the team are now seeking further clarification on this and a decision as to whether this design will be carried forward will be made before the first race".

However, Williams confirmed that no clarification has been issued by the FIA and that it will continue to run the solution as required by its testing schedule. Caterham also stated that "we will continue to work through our test programme as normal" and stressed that it can run any parts it so wishes during the pre-season tests.

The 2013 cars will first have to pass scrutineering on the Thursday ahead of the Australian Grand Prix in Melbourne.