Police investigating suspected doping by the Tour de France team Bahrain Victorious have seized more than 450 capsules of unidentified substances at a house in Slovenia during raids across Europe.

Riders and staff had their homes raided and the team's hotel in Denmark was searched this week ahead of the three-week race which started on Friday in Copenhagen.

In a statement, the European Union Agency for Criminal Justice Cooperation (Eurojust) said 14 properties in six countries were searched and three people were interrogated.

Eurojust said, "412 capsules with undetermined brown content and 67 capsules with undetermined white content" were found at a property in Slovenia, where a mobile phone was also seized.

Substances were also seized in Belgium, Italy and Poland, plus computers, phones and other electronic devices. Police also searched properties in Spain and seized potential evidence.

The investigation was opened in May and led by prosecutors in Marseille, France, Eurojust said, adding the target was "suspected doping violations involving an international cycling team."

The team sponsored by the government of Bahrain also was raided by French police during last year's Tour.

At the Tour, Australian rider Jack Haig, who was third overall at last year's Vuelta a Espana, is co-leader on the road for the eight-strong team's challenge.