As authorities in several countries tried to determine what caused the deadly crash of a passenger airplane in Kazakhstan, investigators and experts Thursday were focusing on the possibility that fire from a Russian air defense system had struck the plane.

Aviation experts cast doubt on a Russian agency’s contention that the Azerbaijan Airlines jet had hit a flock of birds, saying images of the crash site show holes in the plane’s fuselage that appeared unlikely to have been caused by them.

Of the 62 passengers and five crew members on board, 38 were killed, according to Kazakhstan’s authorities.

The jet had been flying Wednesday morning from Baku, the capital of Azerbaijan, to Grozny, in Russia’s Chechnya republic, at a time when drone strikes were taking place around Grozny and Russian air defense systems were responding, according to residents and local news media reports.Two Azerbaijanis briefed on a government inquiry said Azerbaijani officials now believe that a Russian Pantsir-S defense system damaged the plane. They spoke on condition of anonymity because the investigation was ongoing. Caliber, a news outlet in Azerbaijan that is close to the government, also reported that the country’s investigators believe a Russian Pantsir system was responsible.

U.S. intelligence agencies do not have definitive information yet, but U.S. officials said there are preliminary indications that the plane was shot down by a Russian anti-aircraft system, mostly likely a surface-to-air missile.

Moscow reaction

The Kremlin warned Thursday against making any immediate judgments about the cause.

“The investigation is ongoing. We need to wait for its conclusions,” Dmitry Peskov, the Kremlin’s spokesperson, told reporters.

Some Russian pro-military bloggers have also pointed the finger at Russian air defenses. Yuri Podolyaka, a popular blogger, said in a post on Telegram on Wednesday that the airplane likely had been “incidentally shot down by an air defense system.”

Another Telegram channel, Fighterbomber, which is believed to be run by Capt. Ilya Tumanov of the Russian army, posted a video that it said showed it was unlikely that a bird strike had punctured the fuselage. The New York Times verified the video, which shows the tail section of the aircraft resting upside down about 31/2 miles from the end of the airport in Aktau, Kazakhstan. The tail is peppered with dozens of small holes. It is unclear what caused the holes.

Radar jamming

Flightradar24, a flight tracking service, said the Embraer 190 jet had been subjected to radar jamming and spoofing near Grozny, and for part of its journey did not send radar information. Flightradar24 said available data indicated the plane had problems with altitude control, and cited images from the crash site that it said showed “puncture damage” to part of the aircraft.

The plane crashed while trying to make an emergency landing in Aktau, Kazakhstan, about 260 miles east of Grozny, on the shore of the Caspian Sea.

Besides Azerbaijan and Russia, authorities in Kazakhstan said they had opened a criminal investigation into the crash. Kazakhstan’s transportation authority said in a statement Thursday that the plane’s manufacturer, Brazilian jet-maker Embraer, would also be examining the crash along with the Brazilian air force.

Timeline of flight

While en route to Grozny, the flight was diverted because of fog, Russian state news agencies reported. Soon after the crash, Russia’s state aviation authority said the plane had hit a flock of birds, causing it to attempt an emergency landing, the state-run RIA Novosti news agency reported.

But aviation experts and military observers expressed skepticism of that account, citing the recent military activity in the area near the flight path, the available information from aviation sources, and videos and images posted by survivors.

Speaking at a news conference Wednesday, Azerbaijani President Ilham Aliyev said that it was too soon to speculate on the reasons behind the crash, but said that the 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.

Authorities in Azerbaijan, Kazakhstan and Russia were tight-lipped about a possible cause of the crash but a lawmaker in Azerbaijan blamed Moscow. Rasim Musabekov told the Azerbaijani news agency Turan that the plane was fired on while in the skies over Grozny and urged Russia to offer an official apology.

“Those who did this must face criminal charges,” Musabekov was quoted by Turan as saying, adding that compensations to the victims should also be paid. “If it doesn’t happen, relations will be affected.”

The area around Grozny has been the scene of aerial battles in recent weeks involving drones, usually launched by Ukraine, and Russian air defenses. Osprey Flight Solutions, an aviation security company, said in a note to its clients Wednesday that the Azerbaijan Airlines plane had likely been struck by Russian air defenses “during an incident of misidentification.”

Heinrich Grossbongardt, an aviation industry expert in Hamburg, Germany, said that data showing the plane’s trajectory, and footage of the aircraft, suggested that its electrical and hydraulic systems had been damaged, rendering the plane uncontrollable. According to Flightradar24, data received from the plane showed that its vertical speed oscillated more than 100 times during the final 74 minutes of the flight.

“You see an airplane flying wild, wild maneuvers with strong fluctuations in the course and in the flight altitude,” Grossbongardt said in an interview.

Had birds hit the engines, it could have caused them to fail, leading to a loss of power but still leaving the plane controllable. That was what happened Jan. 15, 2009, to US Airways Flight 1549, which struck a flock of birds shortly after taking off from LaGuardia Airport in New York City, he said.

“We saw that on the Hudson River,” Grossbongardt said, referring to the pilot’s ability to successfully land on the water, saving the lives of all 155 people on board. “Here, a flock of birds? No way.”

Azerbaijan Airlines said it was suspending flights from Baku to Grozny and Makhachkala, in neighboring Dagestan, until investigations into the crash had concluded.

This report contains information from the Associated Press.