Russian investigators are not considering terrorism among the most likely causes of a military plane crash believed to have killed more than 90 people, Transport Minister Maxim Sokolov said Monday.

“The main scenarios do not include an act of terrorism. We believe the reasons for the catastrophe could have been either a technical problem or flight error,” Sokolov was quoted as saying by state media.

He earlier said the reason why debris from the crash in the Black Sea had been spread over several kilometres was because of a strong current.

The plane, a Tupolev Tu-154, crashed shortly after take-off on Sunday morning, off the coast of the Russian city of Sochi. The majority of the passengers were from a renowned military band, the Alexandrov Ensemble, on their way to entertain troops in Syria.

A surveillance camera video uploaded to YouTube purported to show a flash of light in the dark sky above Sochi around the time when the plane crashed, prompting speculation that there could have been an explosion.

Last year a Russian commercial airliner travelling from the Egyptian resort town of Sharm el-Sheikh to the Russian city of St Petersburg crashed shortly after take-off, killing more than 200 people.

An affiliate of the terrorist group Islamic State said it placed a bomb aboard that plane in retaliation for Russia’s military campaign in Syria.

Russian President Vladimir Putin, who declared Monday a day of mourning over the military plane crash, expressed “profound condolences” to the victims’ families.

It was Russia’s second national day of mourning in as many weeks, following the shooting of the Russian ambassador to Ankara by a gunman who denounced Russia’s involvement in the Syria conflict.

The first recovered bodies from the crash were flown to Moscow on Monday to be identified, Deputy Defence Minister Pavel Popov said, as a huge search effort continued.

At least 11 bodies have been found.