Russian investigators are searching snow-covered fields near Moscow for clues why a passenger plane crashed. <br/><br/>All 65 passengers and six crew were killed when the Saratov Airlines jet went down minutes after taking off from Domodedovo airport yesterday. <br/><br/>Officials say, they are considering weather conditions, human error and technical failure as possible causes. They did not mention the possibility of terrorism. <br/><br/>The Antonov An-148 was en route to Orsk in the Ural mountains. It crashed near the village of Argunovo, about 80 kms south-east of Moscow. Wreckage and body parts are strewn over a large area. More than 700 people are involved in the search operation.<br/><br/>