As the emergence of mysterious drones continues to baffle law enforcement, Newsweek has mapped the locations where they were most commonly spotted.

In November, New Jersey residents began reporting drone sightings, with the phenomenon recently spreading to New York. On Tuesday, New Jersey Representative Chris Smith said a law enforcement officer “saw 50 drones flying out of the ocean” two nights earlier.

Smith also told Congress that the state’s Coast Guard was once tracked by a fleet of drones while on the water.

He said: “There were a number of other people here last night, including a Coast Guard commanding officer who said that one of their 47ft motor lifeboats was followed by 12 to 30 of these drones as it made its way into the water. Right behind them!”

New Jersey Governor Phil Murphy confirmed that nearly 50 drone sightings were reported across the state on Sunday. He told residents he was taking the incidents “dead seriously.”

Sightings have been reported in three states along the East Coast: New Jersey, New York and Pennsylvania. The largest number was in the Garden State, where drones were spotted in more than five counties.

In December, New Yorkers began reporting drone sightings, with the devices spotted in Brooklyn and parts of Staten Island. On Sunday, Brooklyn residents reported seeing up to 12 drones near the Verrazzano-Narrows Bridge.

Mysterious drones have also been spotted in eastern Pennsylvania, and residents of Philadelphia reported similar sightings.

Newsweek emailed the FBI asking for an update on its investigation into the drones.

The agency has not identified the source or type of devices, with Robert Wheeler Jr., the deputy director of the FBI’s Critical Incident Response Group, telling Congress on Tuesday: “We do not attribute (the sightings) to any individual or group.” However, we are actively investigating and enlisting the help of the interagency (task force) and the public.”

When asked if there was a threat to public safety, Wheeler responded, “There’s nothing known that would lead me to make that statement, but we just don’t know, and that’s the concerning part.”

He added: “We are actively investigating and would like to answer these questions, but I don’t have a better answer.”

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