Azerbaijan Airlines’ Embraer 190 was en route from Baku to the Russian city of Grozny when it was diverted for reasons yet unclear and crashed while making an attempt to land in Aktau in Kazakhstan.

Russian aviation authorities said the Azerbaijan Airlines plane had hit a flock of birds. But some experts cast doubt on that account, pointing to footage showing apparent holes in the fuselage.

There are early indications that a Russian anti-aircraft system may have struck the Azerbaijan Airlines plane that crashed in Kazakhstan, killing dozens, a U.S. official told ABC News. If these indications prove true,