Tragedy again struck the San Marino Grand Prix, turning the Formula One auto race into a terrible weekend of death and destruction.

Three-time world champion Ayrton Senna died Sunday about four hours after crashing into a concrete wall at about 186 mph. Another high-speed crash in Saturday's qualifying killed Austrian rookie driver Roland Ratzenberger.On Friday, Rubens Barrichello's car became airborn, crashed against the barriers and flipped. The young Brazilian sustained a concussion and amnesia and called his survival a miracle.

Senna, the former world champion, had been shocked by Ratzenberger's death and refused to complete qualifying Saturday.

On Sunday, shortly after the Grand Prix race restarted following five laps at slow speed behind the pace car, Senna's Williams Renault car went straight through the Tamburello turn, a spot with a history of bad accidents.

"I don't know what happened to Senna," said Michael Schmacher, who won the race. "I was just behind him, he took two or three bumps and went off. I must add however that he looked very nervous today, from the very first lap.

"It's a sad day. It was so dramatic and I have a bad feeling."

Nelson Piquet and Gerhard Berger were slightly injured in high-speed crashes at the same bend in the late '80s.

Senna was pulled unconscious from the cockpit - his car's right wheel torn off and the front section badly damaged following the impact.

The 34-year-old Brazilian, considered one of the fastest Formula One drivers, was airlifted to Maggiore Hospital of Bologna where he died of massive head injuries.

Senna's crash was not the only drama of the day.

J.J. Lehto of Finland, returning to racing following a neck injury, had the rear part of his Williams Renault destroyed by the Lotus Honda of Portuguese Pedro Lamy at the start. The engine of Lehto's car cut out shortly before the green light was given and Lamy slammed into the racer.

The two drivers were unhurt but seven spectators and one policemen were injured by flying pieces of cars. One of them, Antonio Maino, 28, was reported in serious condition.

Shortly before the race ended with Schumacher sailing to his third consecutive Grand Prix triumph, Italian veteran Michele Alboreto ran down three Ferrari mechanics and a Lotus team official while coming out of the pits, after changing tires. Organizers later said the four received minor bruises.

As the racing world mourned two deaths in as many days, Schumacher said drivers will have to strongly pursue better safety in Formula One races - both for circuits and cars. The deaths were the first on the circuit since 1982 when Italian rookie Riccardo Peletti was killed in Canada.

"Safety must be improved. We are pushing very hard for this but we are aware they cant do it in one day," Schumacher said. "Each track can be dangerous at some points, if something unexpected happens."

Alain Prost, Senna's arch-rival who retired last year after capturing his fourth World title, said "when you crash at 186 mph you can hardly survive."

"There were no deaths in the last few years, despite serious accidents . . . only because of good luck," Prost told Italian television. "Carbon fiber bodies (of race cars) are not indestructible."