A puzzling flurry of apparent drone sightings along the US east coast is “nothing nefarious”, says President Joe Biden.

The sightings in recent weeks have occurred in New Jersey and a number of neighbouring states, sometimes around air bases. The phenomenon has prompted a number of conspiracy theories about foreign involvement.

Authorities have not given many definitive answers, other than to say the sightings are not always of drones, and that they do not believe there is a threat to national security or that a foreign power is at work.

Members of the US House Intelligence Committee, who were given a closed-door briefing on Tuesday, joined Biden on Wednesday in trying to reassure the public.

Among the committee members who spoke to reporters afterwards were Chrissy Houlahan, a Democrat.

“To date, they haven’t found anything that would indicate that there’s foreign influence, foreign actors, or even little green men who are working on the American people,” she was quoted as saying by The Hill.

In his own comments to the media, Biden said: “We’re following this closely, but so far, no sense of danger.”

He stressed that the sightings were not evidence of any wrongdoing. “There’s a lot of drones authorised up there,” he said. “I think one started it and they all – everybody wanted to get in the deal.”

In recent days, the sightings have led to the temporary closures of a Stewart International Airport in New York and of Patterson Air Force Base in Ohio.

Government agencies previously said they had “not identified anything anomalous”. They agreed with Biden that many drones that had been sighted were lawfully flown by hobbyists and law enforcement – adding that people were also spotting “manned fixed-wing aircraft, helicopters, and stars mistakenly reported as drones”.

But questions from the public remain. Earlier in the week, New Jersey man Noel Thomas described to the BBC his experience of spotting a mystery object in the sky. He said it was the size of a school bus, rectangular with blinking lights, and “definitely something I’ve never seen”.

A police officer in the same state said: “We’re just looking for some sound, reasonable answers so that people could go about their life and not live in this hysteria that we have going.”

As the mystery persists, state governments are calling for more power to deal with the small, uncrewed aircraft being spotted in the skies. Earlier this week, New York Governor Kathy Hochul said officials were sending her a drone detection system.

Among those who have voiced their suspicions are President-elect Donald Trump, who has said the government “knows what it happening”, but “for some reason they don’t want to comment”. However, he said he “can’t imagine it’s the enemy”.

The Pentagon earlier denied the suggestion of one New Jersey lawmaker that the possible drones came specifically from an Iranian “mothership”, while an FBI official said there may have been “a slight overreaction” on the topic.