The BMW Sauber team paid the biggest price in an opening qualifying session for the Belgian Grand Prix blighted by the return of the rain after just a few minutes, with the changing track conditions making setting a good enough time something of a lottery.

Vitaly Petrov putting a wheel on the still damp kerb at Liege caused an early red flag as his Renault was retrieved from the barriers and, by the time the action resumed, the rain clouds were over Rivage, bringing chaos as drivers fought for track position and, in some cases, ran out of road.

Times tumbled as the survivors made their way across the line, with Lewis Hamilton eventually pipping McLaren team-mate Jenson Button for top spot but, with the shower abating as quickly as it had arrived, the drying track provided the opportunity for others to redeem their situation.

Sebastian Vettel was the first to recognise the potential of intermediate rubber, hauling himself up from a perilous 17th to third, with Adrian Sutil, Jarno Trulli, Bruno Senna and Heikki Kovalainen doing likewise to escape the drop zone. However, when Robert Kubica went fastest of all, almost everyone was forced to return to the track, shaking up the order.

Sauber's bid to cement its place in Q2 slipped up when both Kamui Kobayashi and Pedro de la Rosa went off, at Rivage and Fagnes respectively, handing the newcomer teams a rare chance to progress. Timo Glock and Heikki Kovalainen were the drivers to take advantage, progressing in 16th and 17th positions, while Senna, HRT team-mate Sakon Yamamoto and Virgin's Lucas di Grassi dropping out.

Nico Rosberg headed namesake Nico Hulkenberg and Rubens Barrichello at the top of the order, with Kubica and Michael Schumacher completing the top five.