A Russian heavy-lift military cargo plane crashed on takeoff Sunday in Siberia, killing all 11 crew members on board, AP qouted officials as saying. The crash was the second in less than a month to involve an Il-76 , the mainstay of the Soviet and Russian air force since the 1970s. These and a string of other accidents have raised concerns about the condition of Russia"s aging fleet of Soviet-built aircraft. The cause of Sunday"s crash was not yet known. The four-engine plane had just taken off from Mirny in the Sakha Republic when it tilted to the right and was unable to gain altitude, said Vasily Panchenkov, a spokesman for the Interior Troops, which were flying the aircraft. The plane hit a slag heap from an old mine and crashed, exploding on impact, he said. The plane, which was headed to Irkutsk, was carrying no cargo but its fuel tanks were full. The Il-76 crashed about a mile (two kilometers) from the runway in open fields. No one on the ground was reported hurt. -- SPA