A large number of mysterious drones been reported flying over parts of New Jersey in recent weeks and have more recently been spotted over New York City, sparking speculation and concern over who sent them and why.

Officials sound alarm over reports of the strange sights—seen over New Jersey, New York, Maryland and Pennsylvania—with one asking for a “limited state of emergency.”

The US government says the flying objects pose no threat to national security, but their origin and intentions remain unclear.