The Day of Mourning for the victims of the plane crash was marked in Azerbaijan on Thursday killed 38 people, and 29 survivors were injured while speculation about the possible cause of the disaster increased.

The Azerbaijan Airlines Embraer 190 was on its way from the Azerbaijani capital of Baku to the Russian city of Grozny in the North Caucasus on Wednesday when it veered for still unclear reasons and crashed while trying to land in Aktau, Kazakhstan, after flying east across the Caspian Sea.

The plane crashed about 2 miles from Aktau. Cellphone footage circulating online appears to have shown the craft descending steeply before hitting the ground in a fireball. Other footage shows part of the fuselage torn from the wing, and the rest of the aircraft lying upside down in the grass.

On Thursday, national flags were flown at half-mast across Azerbaijan, traffic across the country was halted at noon, and signals sounded from ships and trains as the country observed a nationwide minute of silence.

Speaking at a press conference on Wednesday, Azerbaijani President Ilham Aliyev said it was too early to speculate on the cause of the crash, but said weather conditions had forced the plane to change course from its planned course.

“The information I received is that the plane changed course between Baku and Grozny due to worsening weather conditions and headed for Aktau airport, where it crashed after landing,” he said.

Russia’s civil aviation authority, Rosaviatsia, said preliminary information indicated the pilots diverted to Aktau after a bird strike caused an emergency on the plane.

As the official investigation into the crash began, a number of theories emerged as to the possible cause, with some commentators arguing that the holes seen in the tail section of the plane likely suggested it may have been exposed to fire from Russian air defense systems that were fending off a Ukrainian drone strike. .

Ukrainian drones have previously attacked Grozny, the provincial capital of the Russian republic of Chechnya, and other regions in the country’s North Caucasus. Some Russian media claim that there was another drone attack in Chechnya on Wednesday, although this has not been officially confirmed.

Osprey Flight Solutions, a UK-based aviation security company, has warned its clients that “an Azerbaijan Airlines flight was likely shot down by a Russian military air defense system”. Osprey provides analysis for carriers still flying to Russia after Western airlines suspended their flights during war in Ukraine.

Osprey chief executive Andrew Nicholson said the company had issued more than 200 warnings about drone attacks and air defense systems in Russia during the war.

“This incident is a powerful reminder of why we do what we do,” Nicholson wrote online. “It is painful to know that despite our best efforts, lives were lost in a way that could have been avoided.”

Agence France-Presse quoted Russian military expert Yuriy Podolyak as saying that the holes seen in the plane’s wreckage were similar to those left by an “anti-aircraft missile system”. “Everything points to that,” he wrote.

And Gerard Legauffre, a former expert at the French aviation accident investigation agency BEA, also said the wreckage appeared to have “a lot of shrapnel damage,” AFP reports.

He described it as a “reminiscence” of Malaysia Airlines flight MH17, which was shot down by Russian-backed rebels with a surface-to-air missile over eastern Ukraine in 2014.

But when asked about claims that the plane was fired upon by air defenses, Kremlin spokesman Dmitry Peskov told reporters: “It would be wrong to hypothesize before the investigators make their verdict.”

Kazakh Parliament Speaker Maulen Ashimbayev also warned against jumping to conclusions based on images of the plane’s fragments, describing allegations of air defense fire as baseless and “unethical”.

Other officials in Kazakhstan and Azerbaijan similarly avoided comment on the possible cause of the crash, saying that would be determined by investigators.