The director previously said investigators from France, Canada and the US would assist Ukraine in examining the black box.

Iran is flip-flopping on which country will investigate why Ukrainian Airlines Flight 752 crahsed on Jan. 8, killing all 176 people on-board.
On Jan. 18, a director in charge of accident investigations for Iran’s Civil Aviation Organization told an Iranian media organization that he would send the plane’s flight data recorder to Ukraine. The director said his agency had not been able to open or read the device, Reuters reported.
“With the use of the expertise of the countries of France, Canada and America we will try to read the (flight data recorder) in Kyiv,” Hassan Rezaifar, the Civil Aviation Organization director, told Tasnim. “If this effort is unsuccessful then the black box will be sent to France.”
But just a day later, Rezaifar back-tracked on that statement to a different domestic media organization. He told IRNA, which is Iran’s official state news agency, that the black boxes will be investigated locally.
“We are trying to read the black boxes here in Iran. Otherwise, our options are Ukraine and France, but no decision has been taken so far to send them to another country,” Rezaifar told IRNA.
Flowers and candles are placed in front of the portraits of the flight crew members of the Ukraine International Airlines plane shot down by Iran, at a memorial at Boryspil International airport.
Reuters
Often called a “black box”, the flight data recorder helps investigators build a detailed portrait of a crashed plane’s altitude, airspeed, and other crucial details. It also records several hours of audio in the cockpit. 
Two missiles from Iran’s military struck the passenger jet by accident on Jan. 8, which it admitted days after the crash. Previously, officials blamed “human error.”
The plane crash happened after weeks of increased tensions between Iran and the US.
US President Donald Trump ordered the killing of Iran’s top military commander, Maj. Gen. Qassem Soleimani, in an airstrike earlier this month. Iran retaliated last week by firing more than a dozen ballistic missiles at two bases in Iraq hosting US and Iraqi troops. The strikes did not cause any deaths or injuries, but it was only a few hours later when Iran, apparently fearing a US counterattack, shot down the civilian airliner.
Under global aviation rules, Iran has the right to lead the investigation on the flight’s crash. 
However, usually countries work together on such investigations. And Iran has made it clear that the country isn’t intending to follow typical aviation procedures for investigating an international plane crash.
For one, the manufacturer of the plane is usually involved. Iran is refusing to hand over the black boxes to Boeing, a US manufacturer.
“We will not give the black box to the manufacturer and the Americans,” Iran’s Civil Aviation Organisation head Ali Abedzadeh told Mehr, an Iranian news agency.
A woman lays flowers at a memorial of the flight crew members of the Ukrainian 737-800 plane that crashed.
Associated Press
Not many countries have the ability to unlock the flight data recorder. And leaders like Canadian Prime Minister Justin Trudeau have said that Iran is not one of them.
“Iran does not have the level of technical expertise and mostly the equipment necessary to be able to analyze these damaged black boxes quickly,” Trudeau said at a recent news conference in Ottawa. Amid the 176 on the downed plane, 63 were Canadian nationals. 
Trudeau is urging Iran to hand over the black box to France. Ukraine has also pressed Iran to turn over the device, and have said that Iran has violated how the crash site should be treated. 
“Everything was done absolutely inappropriately,” Oleksiy Danilov, the Ukrainian security official overseeing the crash inquiry, previously told The New York Times. He alleged that debris from the crash has been bulldozed.
So far, Abedzadeh said Iran will investigate the crash alone, “but the Ukrainians can also be present.”