LUZ ARDIDEN, FRANCE (REUTERS) - Tadej Pogacar claimed another landmark victory in the 18th stage to edge closer to retaining his Tour de France title as a cloud of doping suspicions hung over the world's greatest cycling race on Thursday (July 15).

Before the start of the stage, the French prosecutor's office said it had opened a preliminary investigation into the Bahrain Victorious team after police searched the outfit's accommodation and bus on Wednesday.

The prosecutor's office in Marseille said the investigation was into "acquisition, transport, possession, import of a prohibited substance or prohibited method for use by an athlete without medical justification."

Bahrain Victorious said they were complying with the investigation.

All Bahrain Victorious riders started the stage but none of them weighed on the race, having been kept up by the searches deep into the night, with Dutchman Wout Poels falling behind Pogacar in the mountains classification.

The Slovenian's brutal acceleration 500 metres from the line, at top of Luz Ardiden (13.3km at 7.4 per cent), could not be matched by his rivals as Denmark's Jonas Vingegaard and Ecuador's Richard Carapaz finished two seconds behind in second and third, respectively.

The result was a carbon copy of Wednesday's summit finish at the Col du Portet, where Pogacar had already beaten Vingegaard and Carapaz in the second of his three stage wins in this year's Tour.

"I can't believe what's happening to me. Today was a really big stage. My legs were not at 100 per cent and I suffered in the Tourmalet," said Pogacar.

"The ascent to Luz Ardiden was tough, too, but I found my rhythm and I had enough energy for the final sprint."

Overall, UAE Emirates rider Pogacar now has a massive advantage of five minutes 45 seconds over Jumbo-Visma's Vingegaard with Carapaz of Ineos Grenadiers in third place overall, a further six seconds behind.

Colombian Rigoberto Uran (EF Education-Nippo), fourth overall at the start, cracked in the penultimate ascent to the Col du Tourmalet to drop out of the top 10.

Australian Ben O'Connor of AG2R-Citroen is now fourth, 8:18 off the pace two days before Saturday's final individual time trial.

Early attackers Matej Mohoric of Bahrain Victorious and world champion Julian Alaphilippe were joined in the ascent of the Tourmalet (17.1km at 7.3 per cent) by a small group featuring French climber David Gaudu.

Gaudu, whose monster work had set up Thibaut Pinot for a landmark win at the Tourmalet in 2019, accelerated and was followed by Alaphilippe, fellow Frenchman Pierre Latour and Portugal's Ruben Guerreiro.

A cooked Alaphilippe was dropped 3.5km from the top with Guerreiro also being left behind two kilometres further up as French president Emmanuel Macron watched from the Tour director's car.

Gaudu broke clear in the descent but he only had a 15-second advantage on an Ineos Grenadiers-led yellow jersey group at the foot of the final climb.

He was caught 9.5km from the line.

Pogacar attacked first, 3.5km from the top, with Vingegaard, Carapaz, Spain' Enric Mas and American Sepp Kuss the only ones to follow.

Kuss flagged before Mas started his sprint 700 metres from the line, only for the 22-year-old Pogacar to speed past him with 500 metres, leaving Vingegaard and Carapaz to fight it out for second after the 129.7km ride from Pau.

In addition to the yellow, Pogacar now holds the white jersey for the best Under-25 rider and the polka-dot jersey for the mountains classification.