The Russian government has warned against spreading “hypotheses” about the cause of the crash of a Russia-bound passenger plane that killed 38 people in Kazakhstan on Wednesday.

Some aviation experts suspected that the Azerbaijan Airlines plane was hit by air defense systems over the Russian Republic of Chechnya, and pro-government media in Azerbaijan quoted officials as saying a Russian missile was responsible.

Before the plane crashed near the Kazakh city of Aktau, it was diverted from its destination in Chechnya to western Kazakhstan via the Caspian Sea.

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

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

In Moscow, Kremlin spokesman Dmitry Peskov said: “It would be wrong to put forward any hypotheses before the conclusions of the investigation. Of course we won’t do that, and no one should do that. We must wait until the investigation is completed.”

The chief prosecutor in Kazakhstan later said that the investigation had not yet come to any conclusions.

However, some commentators in Azerbaijani media say that Azerbaijan expects Russia to admit shooting down the plane.

Several television channels under strict control of the Azerbaijani government began broadcasting interviews on Thursday with experts who spoke openly about the possibility that Russia was responsible.

Broadcaster AnewZ said a preliminary investigation had concluded that the plane was hit by shrapnel from a Russian Pantsir-S surface-to-air missile.

Another pro-government website, Caliber, quoted government sources as saying no one had claimed the plane was deliberately attacked, but Baku expected an apology from Russia.

Asked about the reports, the Prosecutor General’s Office in Baku told the BBC that each version was being investigated.

As it tries not to anger Russian President Vladimir Putin, it will be very difficult for the Azerbaijani government to blame Russia directly unless it admits to shooting down the plane.

It appears that the investigative committee made up of Azerbaijani and Kazakh officials may already have evidence of this, but they are waiting for Russia to announce it first.

Moscow will then have to answer questions such as why Russia did not close its airspace during military activities and why it did not allow the plane to land as quickly as possible – instead of steering it toward Aktau to land.

The Embraer 190 aircraft took off from the Azerbaijani capital Baku on Wednesday morning. The flight was scheduled to go to Grozny, Chechnya, but was diverted due to fog, the airline said.

A surviving passenger told Russian television he believed the pilot tried to land twice in thick fog over Grozny before “the third time something exploded… part of the plane’s skin had flown out.”

The plane was diverted to Aktau Airport, about 450 kilometers to the east. The footage shows the plane heading towards the ground at high speed 3 km (1.9 miles) short of the runway before bursting into flames on landing.

Kazakh authorities have seized the flight data recorder and an investigation is ongoing. Shortly after the crash, Russian state television reports said the most likely cause was an attack by a flock of birds.

But such a collision usually causes the plane to glide toward the nearest airfield, aviation analyst Richard Aboulafia told Reuters. “You can lose control of the airplane, but it doesn’t take you completely off course,” he said.

Justin Crump of risk consulting firm Sibylline said the pattern of damage inside and outside the plane suggested Russian air defenses active in Grozny may have caused the crash.

“If you look at the shrapnel pattern we’re seeing, it looks very much like the detonation of an anti-aircraft missile in the tail and left of the aircraft,” he told BBC Radio 4.

Chechnya has already been hit by Ukrainian drone strikes this month and authorities in neighboring Ingushetia said the Russian region was targeted for the first time since the war began in Ukraine.

A shopping center was reportedly hit when a drone was shot down in nearby North Ossetia, killing a woman.

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

Video footage showed survivors crawling out of the rubble, some with visible injuries.

The injured were taken to hospital. On Thursday, the Azerbaijani news agency Azertac said seven were in good enough condition to fly back to Baku.

Azerbaijan Airlines told reporters that the plane was fully serviced in October and had no technical problems.

Embraer, a Brazilian manufacturer and smaller competitor to Boeing and Airbus, has a strong safety record.