Insurgents exploded a suicide car bomb and launched two mortar shells at Iraq's Interior Ministry during National Police Day celebrations Monday, killing 21 people and injuring 24, police said. Eight US troops and four American civilians died aboard a US Army Black Hawk helicopter that crashed in northern Iraq, the military said Monday. The helicopter, which crashed just before midnight Saturday, was found on Sunday. The military initially said only that there were eight passengers and four crew aboard, all believed to be American. The military on Monday specified that four passengers were civilians. The military said it wasn't yet known what caused the crash and that the investigation into it would take some time. The helicopter went down about seven miles (11 kilometers) east of Tal Afar, a northern city near the Syrian border that has seen heavy fighting with insurgents. The Black Hawk was part of a two-helicopter team providing support for the 101st Airborne Division and was flying between bases when communications were lost, the military said. It was the deadliest helicopter crash in Iraq since a CH-53 Sea Stallion went down in bad weather in western Iraq on Jan. 26, 2005, killing 31 US service members. The first attack on the Interior Ministry was by a suicide car bomber who exploded his vehicle near an entrance checkpoint. Less than an hour later two mortars landed about a kilometer (half mile) from where police were gathered to mark National Police Day. At least 21 people were killed and 24 injured, mostly policemen, said police Sgt. Abdel Hadi Hassan. Several police cars were destroyed in the explosions, and pieces of body parts could be seen on the ground. In other violence Monday, gunmen assassinated an investigative judge in Kirkuk, police Capt. Farhad Talabani said. In Baghdad, gunmen fired on three people working on Iraq's de-Baathification commission, killing one, police Capt. Qassim Hussein said. Gunmen also killed an Iraqi intelligence officer and a doctor in separate attacks, Hussein said. Five bodies bound and blindfolded were found shot to death in Baghdad late Sunday, police said. Five people died in separate attacks in Baghdad on Sunday, including a policeman killed by a suicide car bomber targeting an Interior Ministry patrol. Seven others were wounded. The U.S. military Monday released more details about how a French hostage was freed. As Iraqi army soldiers searching houses for weapons caches Saturday approached a farmhouse west of Baghdad, the captors of the French engineer fled, and Bernard Planche ran to soldiers manning a nearby checkpoint. Iraqi police on Sunday said Planche had been thrown out of a car approaching a checkpoint. Planche, 52, who was working for a non-governmental organization he started himself, was captured Dec. 5. The Defense Ministry in Paris said Planche would return to France on Monday. Results of Iraq's Dec. 15 parliamentary elections will be released after the four-day Islamic feast of Eid al-Adha, which begins Tuesday, said Hussein Hindawi, a member of Iraq's electoral commission. Elections officials Monday canceled a news conference where they had hoped to announce more preliminary results, saying officials were still auditing the results from about 50 ballot boxes and wanted to announce all results at the same time. The leader of Iraq's main Sunni Arab political group said after meeting President Jalal Talabani on Sunday that significant headway had been made in efforts to form a government of national unity. "Talabani and I have an identical point of view regarding the formation of a national unity government based on consensus," Adnan al-Dulaimi said. Al-Dulaimi confirmed that Iraq's two Kurdish leaders, Talabani and Kurdistan regional President Massoud Barzani, have been mediating with other groups to form a coalition government. Their efforts seem to have forged an understanding between the main Shiite religious bloc and al-Dulaimi's group - which represent two traditionally hostile camps whose enmity often threatens to plunge Iraq into sectarian warfare. Shiite leaders have in recent days threatened reprisals against the minority Sunni Arabs following twin suicide attacks that killed more than 100 people. They have blamed the attacks on both the Sunni-Arab-led insurgency and some Sunni Arab political groups they say openly support the militants. "This should be done by consensus for the sake of Iraq's unity and independence. Barzani, Talabani and I agree on this condition, and this is our sole condition and demand," al-Dulaimi said. Talabani said Saturday that Iraq's political groups could form a coalition government within weeks - and some experts say the new government could be formed next month. "Barzani and Talabani are conducting contacts with the Shiite Alliance and I think that the Alliance should agree on this project otherwise stability in Iraq cannot be achieved," al-Dulaimi said of a broad-based government. Forming a viable broad-based government is a key American goal because such an administration, if it includes Sunni Arabs, could help defuse the insurgency.