Iranian state media say officials have found two flight recorders from
the passenger plane that crashed in northwestern Iran Wednesday,
killing all 168 people on board.
A report Thursday said the so-called black boxes were heavily damaged, but experts were still trying to retrieve flight data from them.
Five Russian experts are due to arrive in Iran Friday to help with the crash investigation. Russia's Itar-Tass news agency says the team will be led by top designers from the Tupolev company, the makers of the aircraft.
The Caspian Airlines plane went down as it was heading to the Armenian capital of Yerevan. The plane crashed near the northern Iranian city of Qazvin 16 minutes after taking off from Tehran's Imam Khomeini International Airport.
Iranian state-run television says the last conversation between the plane's pilot and ground controllers was three minutes before the crash.
The report quotes Transport Ministry official Ahmad Majidi as saying the conversation did not indicate anything unusual was happening on the plane.
He also says the process of collecting bodies has ended and the passenger remains will be handed over to their families, following forensic examinations.
Iran's Mehr news agency quotes Majidi as saying a technical problem probably caused the crash.
The United States has extended its condolences to the families of those killed.
The U.S. does not have diplomatic relations with Iran. But U.S. State Department spokesman Ian Kelly says America is working through Swiss diplomats in Iran and the U.S. embassy in Armenia to determine whether any American citizens were on board the aircraft.
Officials said the 15 crew members and 153 passengers were Armenians, Georgians and Iranians.
Armenia declared Thursday a day of mourning.
Iranian President Mahmoud Ahmadinejad has expressed his condolences to the victims' families.
Caspian Airlines is a Russian-Iranian joint venture that was founded in the early 1990s.
Some information for this report was provided by AFP, AP and Reuters.