Two badly damaged black box recorders have been recovered from a Tupolev aircraft that crashed in Iran on Wednesday, killing all 168 people on board, official media reported on Thursday. The cause of the worst air disaster in Iran for six years was still unknown, state television said. Deputy Transport Minister Ahmad Majidi, who is leading the probe into the incident, said it was “likely due to technical problems” as the pilot was experienced, the semi-official Mehr News Agency reported. The aircraft was on its way to Armenia's capital Yerevan when it came down after catching fire in mid-air and ploughing into farmland 16 minutes after departing Tehran. The Russian-built Caspian Airlines plane exploded on impact and left only scattered bits of incinerated metal and fragments of the bodies of 153 passengers and 15 crew across a wide area around a deep smoking crater in the ground. “Because of the severity of the crash, the two black box recorders found are badly damaged, even though they are made of steel,” Majidi told Mehr. “The tapes were out on the ground. We might send the black box to the country where it was manufactured (Russia) to chase the issue with their help,” he said. Majidi said DNA testing would be needed to identify the remains. Most of those onboard were Iranians, but there were also Armenian and Georgian citizens. Eight members of Iran's national junior judo team and two coaches were among the dead. About 40 relatives and friends of the victims planned to fly from Yerevan to Tehran on Thursday, Caspian Airline official Arlen Davudyan told Reuters at Yerevan Airport. Most of them were dressed in black. “I lost by best friend. He was almost a brother...I'm flying to Tehran to pay my condolences to his wife and kids,” said Mehdi Sohrabi, a 27-year-old Iranian who studies in Armenia. Fina Karapetian, an Armenian in her 30s, said her sister and two nephews, 11 and 6, were on board the Tu-154 plane. “Her husband cried on telephone, ‘How will I live without them.' He has no more family,” she said. “My mother and father have almost gone out of their minds.” The United States, Tehran's arch foe, extended condolences on Wednesday to families of the victims. Washington has no diplomatic ties with Tehran but has been trying to engage the country as part of an effort to coax it into negotiations over its disputed nuclear program. US sanctions bar the sale of Boeing aircraft to Iran and hinder it buying other aircraft or spares from the West, many of which rely on US-built engines and parts. Reza Jafarzadeh, a spokesman for Iran's aviation organization, said five specialists from Russia would arrive in Tehran on Friday to help with the investigation. An Iranian insurance company said it would pay 42,000 euros ($58,800) for each victim, state radio reported. Air safety experts have said Iran has a poor record, with a string of crashes in the past few decades - many involving Russian-made aircraft.