By Gilles Le Roc'h

PARIS (Reuters) - Riders who cheat must realize they will get caught, Tour de France director Christian Prudhomme said after news Monday that more riders tested positive on this year's race.

"Police seem to be ahead of thieves, which is something we could not have imagined a few years back," Prudhomme told Reuters Tuesday.

"Those who have cheated must tell themselves that they will get caught," he added.

It was announced Monday that Italian Leonardo Piepoli and German Stefan Schumacher tested positive for the blood-boosting drug EPO on the 2008 Tour.

Prudhomme, who congratulated the French anti-doping agency (AFLD) for its work, said he expected a few more positive tests to be announced shortly.

"I imagine there could be one or two more cases but we are a long way from the list announced by some," he said, referring to media reports that up to 14 positive tests could be revealed.

The International Cycling Union (UCI) also praised the AFLD after the latest positive tests were announced.

"The UCI congratulates the AFLD for the excellent work done on the Tour, which shows that cycling as a whole refuses any form of doping and continues to fight against cheating," UCI said in a statement Tuesday.

(Writing by Patrick Vignal, editing by Ken Ferris)