LONDON -- Formula One racing is a natural home for adrenaline addicts craving speed and excitement.

Yet no F1 driver has ever failed a drug test and it remains a sport in which the cars are far more likely to fall foul of post-race checks.

However last week's announcement by the governing International Automobile Federation (FIA) that Formula 3000 driver Tomas Enge had tested positive in Hungary in August may serve as a warning against complacency.

Enge, the newly-crowned F3000 champion, was a F1 driver last year for three races with the now-defunct Prost team and was the first Czech to break into the top echelon of racing.

A former test driver with both McLaren and Jordan, he expressed shock at his urine sample showing traces of marijuana.

The case may yet have an innocent explanation -- a hearing in Paris will look into that next month -- and the drug in question is not performance-enhancing.

But so-called "recreational" drugs such as marijuana and cocaine can be more serious in a dangerous sport that relies on clear minds, quick reactions and split-second timing rather than muscle and sheer strength.

Australian Mark Webber, a Minardi driver who was in Formula 3000 with Enge last year, had no doubt that F1 needed to stay alert.

"I think that all the guys I'm competing against are, no question about it, totally and absolutely professional," Webber told Reuters. "It wouldn't cross my mind for a minute that there's any of them doing anything to gain performance.

"But they (the FIA) need to control it and keep it there in the back of our minds firmly.

"If the guy (Enge) has been smoking pot and racing a car, he should be out. If Tomas has just tested positive because it's bad luck then that's something that we don't know.

"We enjoy a good time but we're all sensible blokes at the end of the day, I think we don't do anything too outrageous at all.

"I got tested three or four times last year in 3000 and it was an absolute pleasure to give it. I was tested with Tomas last year and everything was fine."

The modern driver has come a long way from the old days, when a champion like the late James Hunt could live the superstar "sex, drugs and rock-n-roll" lifestyle and still perform sensationally on the track.

The days when Le Mans drivers might keep themselves fuelled on champagne to see them through the night and when cigarettes were puffed during pit stops are a part of history.

Fitness is now the key to success.

No grand prix driver has proven positive since drug controls were first introduced in Portugal in 1995.

An FIA spokesman said two tests were carried out per season on a random basis involving six drivers at each and they were processed under International Olympic Committee (IOC) guidelines.

The FIA allows drivers who test positive to compete until proven guilty, arguing that a title can be taken away later, but policies are still evolving as nobody has had to be punished so far.

"I don't know of anyone having failed a drugs test in motorsport, certainly not in Formula One. This is the first time I've ever heard of it," said McLaren principal Ron Dennis at Monza last weekend. "This is not an energy-explosion sport like sprinting."

The lifestyle of some F1 drivers away from the track may cloud the situation.

"I can't think of any drug that would enhance performance and give you an edge," Eddie Irvine wrote in his co-authored autobiography Life in the Fast Lane at the end of his Ferrari years in 1999. "(F1) is not a physical type of thing like athletics. But there is cocaine use amongst certain people who want to party. I party with my own energy and think it's pretty pathetic to take drugs to stay awake.

"However if someone came to me and offered me a safe drug that would give me an edge over my competitors and win me the world championship, I'd think for a moment before refusing.

"The desire to win is overwhelming and can mean people take risks."

Irvine, now with Jaguar, provided one of the more sympathetic voices in Italy at the weekend.

"It could be just that he (Enge) was in a room where people were smoking pot, because it's happened to me where I've been sitting there and I've smelled it immediately I left the room," he told reporters at Monza. "It's very easy to detect and it stays in your system longer than any other drug so it could have been caught that way very, very easily.

"Everywhere you go now, in pubs and walking in the street, there's people smoking away. It's just unfortunate. If you're sitting in a room where there's four or five people lighting up, you're going to get nailed.

"Maybe he didn't think about that. You've just got to have your wits about you.

"No one's ever been caught except for this and it's not performance-enhancing, for sure. I don't know what the level was, but I'd rather give him the benefit of the doubt."