Dozens of schools have been closed in the United States and Great Britain due to threats of explosions received on the telephone, NBC reports referring to the police.

Authorities evacuated thousands of schoolchildren. Schools in 21 US states received threats. According to the threats criminals "mined" in tens of educational institutions of some schools. None of the received messages is yet confirmed.

The majority of calls have one thing in common - they were all automatic. Experts have not yet come to a joint conclusion , some believe that it was a planned action, others haven’t arrived to that conclusion. FBI told  NBC that they are aware of the situation and are ready to help the local law enforcement agencies.