Cycling Tour De France Customs officers in search of banned drugs appear to be keeping a close eye on this Tour de France. Yesterday, five team vehicles were stopped and searched at a toll booth on the A51 motorway near Gap, a level of activity that recalled the scandal-hit 1998 Tour, but there was no sign that anything suspicious was found.

The cars, belonging to the French teams AG2R and Bouygues Telecom, the Swiss squad Phonak, Spain's Liberty Seguros and Belgium's Davitamon, were travelling from the start in Briancon to the finish by roads marked out by the Tour organisers for vehicles wishing to avoid the race route.

The police have a job to do and we should let them do it, said six-time winner Lance Armstrong, whose tenure of the yellow jersey was not threatened yesterday.

There was no indication that these were targeted searches. Indeed, the transport of drugs in team vehicles appears to have ceased after the Festina episode; recent seizures of banned substances have tended to be from unmarked vehicles driven by relatives of the cyclists, such as the 2002 cases involving the Tour's third finisher, Raimondas Rumsas, and his wife, Edita, and the discovery of drugs in a camper van driven on that year's Giro d'Italia by the father-in-law of the Italian cyclist Ivan Gotti.

In the latest episode, the Italian Dario Frigo and his wife, Susanna, were yesterday placed under formal investigation on charges of "aiding and abetting in the use and importation of doping products". Frigo had been detained on Wednesday morning after the arrest of his wife when 10 capsules of what appeared to be banned drugs were found in her car on Monday evening.

Yesterday's stage winner, David Moncoutie, is happy to voice his opposition to the use of even legal products such as glucose drips. He said yesterday the Frigo episode reinforced a feeling that, although all drug tests up to stage eight of the race have been confirmed as negative, riders may not be competing on a level playing field against some of their fellows who have not learnt the lessons of 1998.

"I have no proof; this is a delicate subject and I don't want to create any polemics," he said. "But there is a lot of disappointment among the French at the moment. The speed of the race is extremely high and you can draw your own conclusions."

Yesterday, the average speed was almost 28mph (45km/h), but that was largely because the course was mainly downhill as the valleys gradually widened and the mountains on either side became gentler, with ski-lifts and high Alpine pasture giving way to the lavender fields for which this spa town is famous.

Bastille Day had brought out the crowds and the tricolour flags and, as always, the fête nationale fired up the home cyclists whose race had, thus far, been disastrous. There is no longer a single French cyclist with the public profile of the worthy but charisma-free Laurent Jalabert or the housewives' choice with the dodgy past, Richard Virenque, both now analysing the race for competing television stations. The ageing Christophe Moreau, lying third overall, is no substitute.

The colours of Moncoutie's Cofidis team - led by Britain's David Millar until his sacking over drugs last year - could not have been more appropriate: red, white and blue. He was, it could be said, wrapped in the tricolour, albeit one carrying the freephone number of his sponsor, as he went over the day's final climb, the Col de Corobin, in a move that closely resembled his victory of last year in his native Lot.

To warm the hackles of national pride still further, Moncoutie rode the final kilometres yesterday on the Route Napoleon, the road taken by the Emperor on his return from Elba during the "100 days" of 1815. The Tour's current ruler, Armstrong, has only 10 days of his reign remaining, but there is no sign of any Waterloo on the horizon.

The only concern for the Texan was the loss of one of his chief lieutenants, Manuel "Triki" Beltran, who fell and was taken to hospital. There was another high-profile casualty, the double stage winner and points leader Tom Boonen, who damaged a knee in a crash on Wednesday and did not start yesterday.

Today's stage across the Midi is the only truly flat stage before Paris, and as the mercury nudges 40, it will be hot in every sense.