Officials in Russia and Kazakhstan are urging people to wait for an investigation into the deadly Azerbaijan Airlines plane crash before assigning blame.

Kazakh authorities have recovered the flight data recorder and an investigation is under way. Shortly after the crash, reports from Russian state-controlled TV said the most likely cause was a strike from a flock of birds.

In the crash’s aftermath, Azerbaijan has unleashed rare and stinging criticism of Russia, with the country’s president saying Moscow’s response has caused “surprise, regret and rightful indignation.”