Baghdad (CNN) -- An Iraqi court has cleared a Lebanese militant once held by U.S. forces in the deaths of five U.S. soldiers, saying there wasn't enough evidence against him, an official with Iraq's judicial council told CNN.
Ali Mussa Daqduq's case will be automatically appealed and he will remain in custody until a decision on the appeal is made, said the official, who spoke on the condition of anonymity because of the sensitivity of the issue.
U.S. officials say Daqduq organized a kidnapping in the Iraqi city of Karbala in January 2007 that left five U.S. soldiers dead.
Officials said he was a 24-year veteran of Hezbollah who had commanded a special operations group sent to Iraq to develop "special groups" within Shiite militia. U.S. forces captured him in 2007.
The court cleared Daqduq last week.
In a letter sent Thursday, Republican members of the Senate Judiciary Committee expressed worry that the decision means Daqduq could soon go free, and pressed the Obama administration about its plans for dealing with the Lebanese citizen, who had been held in U.S. custody until the United States ended its military mission in December and handed him over to Iraqi authorities.
"Now an Iraqi court has cleared Daqduq of any criminal charges under Iraqi law and, as we and many other observers had feared, (he) may be set free without being held to account for his crimes against the United States and its soldiers," the senators wrote.
Although Daqduq has been charged with war crimes by U.S. officials, according to the senators' letter, they said the administration had dawdled in acting against him until he was out of U.S. custody and potentially out of reach.
There was no immediate response from the administration.