Senior European Parliament members proposed setting up an investigative committee to determine whether US intelligence agents held terror suspects in secret prisons in Europe. Leaders of the political blocs in the European Union assembly said Wednesday that they will determine the mandate and makeup of the committee early next month and put the proposal to a vote at the parliament's January plenary session in Strasbourg. Speaking to parliament before the decision to launch the inquiry, EU Justice Commissioner Franco Frattini told lawmakers that there was still no proof that detainees had been illegally held in Europe or transferred to other countries via EU territory. He cautioned against drawing conclusions without firm evidence. "There is no evidence confirming allegations that have been made. Finding out the truth means getting evidence. No accusations can be considered founded without evidence," Frattini said. The lead investigator in a separate probe by the Council of Europe said on Tuesday that there were mounting indications that the United States illegally held detainees on the continent and then hurriedly transported remaining prisoners to North Africa when word leaked out. Swiss investigator Dick Marty told the legal affairs committee of the council's parliamentary assembly that a one-month investigation had unearthed "clues" that Poland and Romania were implicated - perhaps unwittingly - in the secret transport of prisoners. Frattini said that Marty deserves "public admiration and support for the activities he carries out." But Frattini said he accepted denials of involvement from Poland, Romania and other European governments. "I can't call into question, without evidence to the contrary, the credibility of member governments. That doesn't exclude our shared desire to seek the truth," Frattini said. Green deputy Kathelijne Buitenweg demanded that Frattini reveal the precise content of responses he received from EU member states to the assembly's questions about the allegations. "Are you happy with the answers? Can you tell us what the content was? If you really want to find the truth, what is your strategy?" she asked. "You say people are not being tortured. Well, people are being virtually drowned, is that not torture? Perhaps you are misinformed," she said.