A passenger plane bound for Russia crashed in Kazakhstan on Wednesday, killing 38 people, and the Russian government warned against promoting “hypotheses” about its cause.

Footage of the crashed fuselage appeared to show shrapnel damage, and some aviation experts believe the Azerbaijan Airlines plane may have been hit by an air defense system over the Russian republic of Chechnya.

The plane was diverted across the Caspian Sea from its destination in Chechnya to western Kazakhstan before crashing near the Kazakh city of Aktau.

29 of the 67 people on board survived. Azerbaijan marked a national day of mourning for the victims of the crash on Thursday.

“This is a huge tragedy that has become a great sorrow for the Azerbaijani people,” President Ilham Aliyev said on Thursday.

In Moscow, Kremlin spokesman Dmitry Peskov said: “It would be wrong to raise any assumptions before the investigation has concluded. We certainly will not do that and no one should do that. We need to wait until Investigation ended.” Complete. “

An Embraer 190 aircraft took off from Baku, the capital of Azerbaijan, on Wednesday morning. The airline said the flight was originally bound for Grozny, Chechnya, but was diverted due to heavy fog.

One surviving passenger told Russian television he believed the pilot tried to land twice in thick fog over Grozny before “an explosion occurred the third time… and some of the skin was blown off”.

The plane was diverted to Aktau Airport, about 450 kilometers (280 miles) east. Video showed the plane hurtling toward the ground at high speed 3 kilometers (1.9 miles) from the runway before bursting into flames as it landed.

Kazakhstani authorities have recovered the flight data recorder and an investigation is ongoing. Shortly after the crash, Russian state television reported that the most likely cause was an attack by a flock of birds.

But aviation analyst Richard Aboulafia told Reuters such collisions would typically cause the plane to slide toward the nearest airport. “You might lose control of the plane, but you’re not going to go wildly off course,” he said.

Justin Crump of risk consultancy Sibylline said damage inside and outside the plane suggested Russian air defense systems active in Grozny may have contributed to the crash.

He told BBC Radio 4: “If you look at the shrapnel pattern we saw, it looked very much like an anti-aircraft missile exploding at the rear and left side of the aircraft.”

Chechnya has been hit by Ukrainian drone attacks this month, and authorities in neighboring Ingushetia said the Russian region had been targeted for the first time since the start of the war in Ukraine.

A drone was reportedly shot down near North Ossetia and a shopping mall was attacked, killing a woman.

Kazakhstan Senate President Ahimbayev Molun stressed that the cause of the plane crash near Aktau is still unclear.

“None of the countries Azerbaijan, Russia or Kazakhstan are interested in hiding information. All information will be made available to the public,” he said.

The passengers on board were mainly Azerbaijani nationals, but there were also some passengers from Russia, Kazakhstan and Kyrgyzstan.

Video showed survivors crawling out of the wreckage, some with visible injuries. The injured are being treated in hospital, with 11 of them in intensive care, AFP reported.

Embraer is a Brazilian manufacturer that is a smaller competitor to Boeing and Airbus but has a good safety record.