Moscow’s sky was back to normal Friday after a mysterious green cloud that descended on part of the city and prompted emergency calls from residents fearing a chemical spill had dissipated.
But nothing so sinister as chemical agents were at hand. Experts allayed worries by explaining that the fog was nothing more than a burst of one of nature's clearest signs that spring has come — pollen.
"High heat, which came to the Moscow region with an intense wind, caused the formation of a large amount of pollen that, mixing and moving in the air, can form such a cloud," an unidentified city official told Interfax.
This didn't stop users of social networks from expressing their alarm.
"Massive green ashes cover Moscow. Rumors on chemical accident. Witness reports on dozens of ambulances driving to the Garden Ring," finance blogger @russian-market wrote on Twitter.
Alarmed callers flooded emergency lines as well. In the neighboring Tula region, citizens called to voice concerns that green dust coating windows and cars was connected to a large chemical plant nearby, although authorities said that a check debunked the idea.
In a disturbing coincidence, Thursday also marked the 26th anniversary of the 1986 Chernobyl disaster that sent a cloud of radioactive dust across several countries in Europe.
The primary culprit on Thursday was pollen from birch trees, whose levels are four times higher than normal, allergy specialist Anatoly Ponamaryov told Interfax. He advised allergy sufferers to remain at home for the time being and take medication for up to 30 days until the heaviest pollen period subsides.