AMSTERDAM, May 30 (Reuters) - Three men in the Netherlands have been arrested on suspicion of drugging, raping and then injecting other men with their own HIV-infected blood during sex parties, Dutch police said on Wednesday. Two of the men have confessed to intentionally injecting their blood, which tested positive with the AIDS-causing virus, into victims' veins against their will, police in the northern Dutch city of Groningen said in a statement. Lawyers for the detained men were not immediately available for comment. Some victims told the police they feared being infected with HIV during forced and unprotected sexual assaults after being drugged. Police began investigating the gay parties after receiving tips, some from AIDS groups. The police confiscated several litres of GHB, sometimes known as a "rape drug" used to make people unconscious, as well as thousands of ecstasy pills, photographs and other evidence. A court in Groningen on Wednesday ordered the suspects to be held in prison for at least 90 days.