What caused the Azerbaijan Airlines crash? Here’s what we know so far.

Officials are trying to determine what caused the Azerbaijan Airlines plane crash in Kazakhstan on Christmas Day that killed 38 people on board, leaving 29 survivors, as speculation mounts that Russia’s military could have had a role in the disaster.

Here is what we know so far:

How did the plane crash?

Azerbaijan Airlines Flight 8243, an Embraer 190 aircraft, was flying from the Azerbaijani capital of Baku to the city of Grozny in Russia’s North Caucasus region on Wednesday when it was diverted for reasons that aren’t yet fully clear.

It crashed while trying to reach another airport in Aktau, in western Kazakhstan. 

Cellphone footage appears to show the aircraft making a steep descent before hitting the ground and exploding in a fireball about two miles from the Aktau airport.

Photos from the scene show the rear portion of the plane’s fuselage still intact after the crash, lying upside down in a field.

The airline said 67 people were on board — 62 passengers and five crew members — and 38 people died in the crash, but 29 of those on board survived.

Investigators have recovered both of the so-called black boxes, the flight data and cockpit voice recorders, from the crash site.

Why did the plane change course?

There were conflicting accounts of why the plane’s pilots diverted the aircraft. 

Russia’s civil aviation authority, Rosaviatsia, initially said it appeared the pilots diverted to Aktau after a bird strike. Later, Russian and Azerbaijani officials suggested the plane had been rerouted due to fog or bad weather in Grozny. Then Russia also said Ukrainian drones targeting the Grozny area were a factor.

Speaking at a news conference Wednesday, Azerbaijani President Ilham Aliyev said that while it was too soon to know the cause of the crash, bad weather had forced the plane to change from its planned course.

“The information provided to me is that the plane changed its course between Baku and Grozny due to worsening weather conditions and headed to Aktau airport, where it crashed upon landing,” he said.

Dmitry Yadrov, the head of Rosaviatsia, said Friday that as the plane was preparing to land in Grozny in deep fog, Ukrainian drones were targeting the city, prompting authorities to close the area to air traffic.

Yadrov said that after the captain made two unsuccessful attempts to land, he was offered other airports but decided to fly to Aktau in Kazakhstan, across the Caspian Sea, instead.

What do officials and aviation experts say about a possible cause?

Kazakhstan, Azerbaijan and Russia all opened investigations into the cause of the crash. The Kremlin has urged people not to jump to conclusions. 

In a statement on Friday, Dec. 27, Azerbaijan Airlines said the plane experienced “external physical and technical interference,” but did not say where it believed the interference came from or provide any further details. It announced the suspension of flights to several Russian airports.

A U.S. official told CBS News there were early indications a Russian anti-aircraft system may have struck the plane in a region where Ukrainian and Russian forces have traded drone and rocket fire for months. The official, who spoke on the condition of anonymity, said if that proved to be true, it would further underscore Russia’s recklessness in its ongoing invasion of Ukraine.

White House National Security Council spokesman John Kirby said Friday that U.S. officials “have seen some early indications that would certainly point to the possibility that this jet was brought down by Russian air defense systems.”  

He confirmed to reporters that the U.S. has intelligence or information pointing to the possibility, but said Kazakhstan and Azerbaijan are currently conducting the investigation and the U.S. will “respect that process.”

Meanwhile, independent aviation experts cast doubt on the bird strike theory, and some pointed to damage seen on the plane’s fuselage as evidence it may have come under fire.

“It certainly does not look like a flock of birds,” said CBS News aviation safety analyst Robert Sumwalt, a former chairman of the National Transportation Safety Board.

“Birds don’t fly at the type of altitude that the initial damage occurred on this airplane,” added Sumwalt.

Yan Matveyev, an independent Russian military expert, noted that images of the crashed plane’s tail reveal the damage compatible with shrapnel from a small surface-to-air missiles, such as the Pantsyr-S1 air defense system. 

“It looks like the tail section of the plane was damaged by some missile fragments,” he said.

Speaking to reporters on a conference call Dec. 27, Kremlin spokesman Dmitry Peskov declined to comment on the claims of possible Russian involvement in the crash, saying it would be up to investigators to determine the cause.

Survivors heard noises before crash

Passengers and crew who survived the crash told Azerbaijani media that they heard loud noises on the aircraft as it was circling over Grozny.

Flight attendant Aydan Rahimli said that after one noise, the oxygen masks automatically released. She said that she went to perform first aid on a colleague, Zulfugar Asadov, and then they heard another bang.

Asadov said that the noises sounded like something hitting the plane from outside. Shortly afterward, he sustained a sudden injury, like a “deep wound, the arm was lacerated as if someone hit me in the arm with an ax,” he said. He denied a claim from Kazakh officials that an oxygen canister exploded inside the plane.

Two other survivors recounted hearing explosions before the plane went down: Jerova Salihat told Azerbaijani television in an interview in the hospital that “something exploded” near her leg, and Vafa Shabanova said that “there were two explosions in the sky, and an hour and a half later the plane crashed to the ground.”

contributed to this report.