Formula One driver Ralf Schumacher left a Milan hospital Wednesday, a day after his car flipped over during testing at the Monza racetrack.

Schumacher planned to return to his home in Salzburg, Austria, to rest and is expected to race in the Sept. 14 Italian Grand Prix at Monza, said Thomas Hofmann, who represents the Williams-BMW driver.

The cause of the crash Tuesday was being investigated but Silvia Hoffer, a spokeswoman for the team, said "we believe it was not a driving error."

Spanish driver Marc Gene will complete the tests for the Williams-BMW team before Schumacher's expected return to Italy next week.

"We will have another chassis at the test and Marc Gene will step in to run that," said a spokesman for the championship leading team.

"Juan (Pablo Montoya) and Marc will complete the program."

Ralf's spokesman Tomas Hoffman said that the 28-year-old, fourth overall in the title standings and 14 points behind older brother Michael with three races to go, had been ordered to rest until Monday.

"He'll fly back to Salzburg now," he said. "He's fine, some concussion but that's all.

"He has to rest until Monday, slow down and do nothing, lying in bed and then he can train again for next week's race."

The tests are the first for the 10 Formula One teams since a six-week summer ban ended and the only chance to try out developments before next week's Italian Grand Prix at the circuit.

They are of crucial importance to those, such as Williams, who use Michelin tyres after doubts were raised about the legality of their tread dimensions.

Ferrari's Schumacher, chasing a record sixth title, is just one point clear of Colombian Montoya and two ahead of McLaren's Kimi Raikkonen. Williams are eight points clear of Ferrari in the constructors' standings.

Information from the Associated Press was used in this report.