TEHRAN - The misalignment of the missile guidance system and a decision to fire without authorization led to the accidental downing of a Ukrainian passenger plane in January, Iran's Civil Aviation Organization has said.

"After the relocation of one of the air defense units of Tehran, clearly causing a change in its heading, a failure occurred due to a human error in following the procedure of system north alignment," the civil aviation agency said in a report on Saturday, adding that "such a functional failure initiated a hazard chain, which, of course, could" have been controlled provided "other planned measures are implemented."

Another key error also contributed to the crash. After spotting the unit and notifying the command about the object, the operator fired a missile at the target "without receiving any response from the Coordination Center."

"Under the applicable procedures, if the defense system operator cannot establish communication with the Coordination Center and does not receive the fire command, they are not authorized to fire," the report said.

"The sequence of events clearly shows the occurrence of a chain of events initiated by a human error," it added.

The agency noted that the report "does not entail the final conclusion of the accident investigation" and the investigation is still in progress.

The Ukraine International Airlines Flight 752 crashed just minutes after taking off from Tehran's Imam Khomeini International Airport on Jan. 8. All 176 passengers and crew members on board the Boeing 737-800 aircraft were killed.

The Iranian military later admitted that they mistook the Ukrainian jet for a hostile plane and "unintentionally" shot down the plane.