Israel Aircraft Industries flatly denied Thursday reports from India that its spy drones were prone to crashes. New Delhi has complained to Israeli officials over the high crash rate of their unmanned aerial vehicles, the Associated Press reported. At least four of the 50 Searcher and Heron type UAVs have crashed in the past two years, Defense Minister Pranab Mukherjee informed the Indian parliament, according to the Press Trust of India news agency. According to PTI, Mukherjee said investigations attributed the crashes to systems failure. In one of the crashes, an Indian air force handler was reportedly killed. Mukherjee reportedly said that state-owned Israel Aircraft Industries who manufactured the UAVs had agreed to repair them for free. "A continuous and multifaceted effort is under way in the defense forces to enhance and upgrade safety of the UAV's," Mukherjee wrote in a letter to the parliament quoted by AP, and he added that measures to enhance the quality of training were also being pursued. Officials at IAI were stunned by the report. "We flatly deny this," said Ya'ir Dubester, director of IAI's Malat division, which manufactures the Searcher and Heron. "Not one of our UAVs has ever crashed in India." The UAVs are deployed along India's border with Pakistan and in the strife-torn Himalayan region of Kashmir. Analysts have noted that the accident-prone Indian air force has one of the highest attrition rates in the world. Last year, India ordered three Phalcon airborne early warning aircraft from IAI for $1 billion, the largest one-time arms sale in the history of the state. India is Israel's leading arms buyer and ties between the two countries have warmed considerably this decade.