The two Williams of Juan Pablo Montoya and Ralf Schumacher topped the timesheets after a frantic end to the first of Saturday's practice sessions, ahead of qualifying for the San Marino Grand Prix.

After yesterday's wet conditions, the sun had returned to Imola for Saturday morning. However the track was still slightly damp from overnight rain, prompting most drivers to use intermediate tyres.

The Bridgestone runners and in particular Ferrari dominated early on, but as the track continued to dry the Michelin teams came good with Williams snatching a one-two in the final minute of the session. David Coulthard also jumped up the order to briefly top the times before finishing third for Mclaren.

Michael Schumacher ended the 45-minute session fourth fastest, ahead of Heinz-Harald Frentzen, who was again impressive in the Arrows. Jacques Villeneuve completed the top six for BAR.

Although the track was drying it was still slippery enough to catch several drivers out. Jordan's Giancarlo Fisichella and Jaguar's Pedro de la Rosa both ended their sessions in the gravel, the latter having failed to set a time.