A cluster of vehicle bombs detonated simultaneously Tuesday in the Taleban's spiritual homeland near a foreign-owned construction company that had recently taken over a contract to build a road through an insurgent-held area. At least 41 people were killed, all civilians, officials said. The thundering explosion occurred just after nightfall in a district that includes UN facilities and an Afghan intelligence office. The force of the blast shattered windows around the city and sent flames shooting into the sky. So many houses and nearby buildings had collapsed that officials feared the death toll could rise further. At least 66 people were wounded, said Gen. Ghulam Ali Wahabat, a police commander in charge of southern Afghanistan. “There was big smoke in the sky, and there were many dead bodies,” said Mohammad Ismail, a vegetable seller being treated at the hospital for leg and hand injuries from the blast. “Some of the wounded were crying out.” It appeared the main target was the Japanese company that is involved in reconstruction efforts in the southern Afghan city. The company recently took over a contract to build a road that insurgents had stalled for several months. An intelligence office is about a quarter mile (400 meters) from the attack site and a UN office is located about a half mile (800 meters) away. “The staff is good, everybody is safe,” said Samad Khaydarov, head of the U.N. Assistance Mission in Afghanistan. “Our office, our guesthouses, are safe. ... Unfortunately, security is not so good in Kandahar.” No one immediately claimed responsibility for the attack. The blast in the center of the city was one of the largest since the Taliban were expelled from the country in 2001. It destroyed about 40 shops, including restaurants and bakeries. “Once again they've killed children, women, innocent Afghans. They are not human. They are animals. You can see for yourself the destruction of this enemy,” said deputy provincial police chief Mohammad Sher Shah. The exact mechanism of the bombing was still being determined. Provincial council member Haji Agha Lalai said five vehicles filled with explosives detonated together, causing the massive blast. But Shah said the vehicles used were an oil tanker filled with explosives and two car bombs. Kandahar is the spiritual home of the Taleban, and the militants have carried out several complex attacks here in the last several years. A large NATO base sits on Kandahar's outskirts, but militants control districts immediately to the city's west. In other violence, a bomb blast killed four US troops in southern Afghanistan on Tuesday, said military spokeswoman Lt. Cmdr. Christine Sidenstricker. No other information was released pending the notification of family members. The deaths bring to 41 the number of US troops killed in Afghanistan this month, the second deadliest month in the country since the 2001 US invasion. Last month a record 44 US troops died. Karzai, top rival about even President Hamid Karzai and his main rival, former Foreign Minister Abdullah Abdullah, were running virtually even Tuesday in the first fragmented returns from last week's Afghan election, raising the possibility of a runoff that could drag the process out for months. The figures came from 10 percent of the more than 27,000 polling sites nationwide _ too small a sampling either to draw a conclusion about the outcome or silence criticism that the ballot was marred by fraud and Taliban violence. The United States and its NATO partners had hoped Thursday's election would produce a clear winner with a strong mandate to confront the growing Taliban insurgency, widespread corruption, narcotics and a stagnant economy.