Two years ago, a cyclist on the Tour de France quietly admitted he was using small quantities of the red blood-cell generator erythropoietin on a daily basis. Not to win or help a team-mate to win, merely to keep up. "If you're in a war and everyone is using machine-guns, you need to go out armed at least with a pistol," he said.

When the story was told a few months later to Hein Verbruggen, head of cycling's governing body, the Union Cycliste International (UCI), he did not seem perturbed but saw the rider in question as a weak-bodied aberration. That seemed a pious hope at the time, and the more so after the events of the past 10 days.

What French customs men found three days before the start of this year's Tour, in one of the Fiats issued to the world's number one-ranked team, Festina Watches, was the heaviest of heavy artillery: three brands of erythropoietin, plus human growth hormone and two kinds of testosterone-based steroids.

The masseur driving the car, a 53-year-old Belgian named Willy Voet, was apparently on his way to the start of the Tour in Dublin. He claimed he was acting on the orders of the team management and that he had been given this kind of commission in the past.

This is the first time that erythropoietin, commonly known as EPO, has been linked to a major cycle race, and it backs up allegations made in the past few years by former professionals that the hormone is in wide circulation in professional cycling.

Eprex, one of the brands of EPO found in Voet's car, was what was offered to Nicolas Aubier, who was a team-mate of Britain's Chris Boardman. Aubier, who stopped riding as a professional in 1996, told the French newspaper L'Equipe that he could think of only one top rider who was not using EPO or human growth hormone: Boardman.

Aubier's testimony, backed up by that of the former Tour stage winner Gilles Delion, came hot on the heels of a report delivered to the Italian Olympic Commission during 1996 by Dr Sandro Donati. The report was shelved but was leaked to the Italian press. It named a raft of top Italian cyclists and their trainers as users and suppliers of EPO, allegations which were universally denied.

Donati remains convinced that the traffic in EPO in cycling is worth millions of pounds; he has said that one pharmacy in Tuscany sold £60,000 worth of the drug in six months.

The standard defence in cycling circles at allegations such as those made by Donati, Delion and Aubier is that these men are twisted failures who are taking out their frustrations on the sport. The response was the same in 1990 when Paul Kimmage, the former Irish professional, stated that amphetamines were still in occasional, casual use.

The importance of the Festina seizure, their expulsion from the Tour, and the police investigation into the team's directeur sportif, Bruno Roussel, and team doctor Eric Rijckaert, is that the French justice system cannot be accused of having an axe to grind. Nor can the Italian drugs police, who last year found human growth hormone, anabolic steroids and syringes in a team hotel during the Tour of Italy.

It is 30 years since drug tests were introduced to cycling after the death of the British cyclist Tom Simpson in 1967 from heat exhaustion which may have been linked to his ingestion of amphetamines.

Compared with the number of tests carried out, the proportion of positives is small, and officials such as Verbruggen have argued that this means drug taking cannot be said to be rife in cycling.

But drugs such as EPO and human growth hormone cannot be detected by current testing methods. Last year, the UCI brought in random blood tests. If a cyclist is found to have blood thicker than a set limit - which can be caused by altitude training or simple dehydration, as well as by EPO - he is prevented from racing. But the tests do not confirm the presence of EPO, and it has been argued that they simply restrict its abuse, not its use.

The nine Festina riders in the Tour said none of their number has failed a drug test on this Tour - although the Frenchman Christophe Moreau has an appeal pending against a positive for steroids - and that they should be presumed innocent until French justice has run its course. The Tour organisers and the UCI were, until last night, of the same opinion.

For all the messages of support along the route on banners with messages such as "Festina we are with you", and "Just win the Tour, don't worry about the rest", the team had been in limbo.

"It's doing my head in," the team's Australian domestique, Neil Stephens, had said yesterday morning. "I don't want to be here any more; I saw a crash the other day and almost steered for it so I could go home."

On Thursday his team leader, Richard Virenque, France's most popular cyclist, was angry when questioned about the affair. "Don't turn it into a detective story," he pleaded.

But a detective story it is, Inspector Maigret in real life, at the heart of France's greatest summer institution. The country is gripped by the Festina policier, and no one can predict the denouement.