Sebastian Vettel hit another obstacle in his already troubled Formula One title defense when his Red Bull sputtered to a stop early in the Spanish Grand Prix's first practice session on Friday.

Lewis Hamilton steered his Mercedes to the fastest lap time of 1 minute, 27.023 seconds, while teammate and F1 leader Nico Rosberg was limited to only nine laps due to a cooling issue.

Vettel was running through his fifth lap on the 4.6-kilometer (2.9-mile) Circuito de Barcelona-Catalunya when an electrical problem caused his Red Bull to stop.

Vettel helped push his RB10 out of the path of his rivals before a group of fans gathered at the fence to take photographs of the four-time world champion using a fire extinguisher on the back of his malfunctioning car.