Zelensky said earlier the possibility that a missile downed the Ukrainian Boeing 737, killing all 176 people board, had not been ruled out but it had not been confirmed yet.
Victims onboard flight PS752 included 82 Iranians, 63 Canadians and 11 Ukrainians as well as nationals from Sweden, the UK, Afghanistan and Germany.
He added that it was possible that this was unintentional.
He said would discuss the investigation with US Secretary of State Mike Pompeo later today.
But unidentified officials told U.S. media that satellite, radar and electronic data indicated Tehran's air defence units downed the aircraft.
He added that the investigation team was still waiting for information from the aircraft's black box.
The black boxes - that are actually bright orange - are seen sitting inside a crate, handled by the officials with the Iranian Civil Aviation Organization (CAO).
The crash came just hours after Iran carried out missile strikes on two airbases housing United States forces in Iraq. Washington killed an Iranian general last week in a drone attack in Iraq, prompting Tehran's missile launches.
Abedzadeh also said that the plane's pilot had called the control tower prior to turning back toward the airport but that the engine caught fire in mid-air and the plane crashed about two minutes later.
The report also said that both of the plane's black boxes - which record flight data - had been recovered for analysis, although they had sustained some damage.
Iran's foreign ministry earlier invited USA plane maker Boeing to "participate" in the probe.
Ukrainian investigators had a good meeting Thursday with their Iranian counterparts, who proposed, among other things, that Iranian technicians would decrypt the information while the Ukrainians observed, Shevchenko said.
"Iran's AAIB is the lead investigative agency and questions regarding the progress of the investigation should be directed there. To do so, our experts must receive unconditional support for their investigation".