The governor of New Jersey has demanded that Joe Biden take control of an investigation into mysterious and more frequent appearances of multiple large drones flying over his state amid mounting frustration that federal officials are downplaying the incidents.

Democrat Phil Murphy released on Friday a letter he wrote to the White House to express his “growing concern” after representatives from the Pentagon and FBI ruled out involvement by the US military, or hostile foreign actors, in numerous sightings of unexplained flying objects above about a dozen counties since the middle of November.

“It has become apparent that more resources are needed to fully understand what is behind this activity,” he wrote in the letter, published the same day that reports emerged of multiple drones breaching airspace at Naval Weapons Station Earle in Monmouth county.

“I respectfully urge you to continue to direct the federal agencies involved to work together until they uncover answers as to what is behind the UAS [unmanned aircraft systems] sightings.”

Annoyance has been growing among politicians and law enforcement in New Jersey following proliferating reports of drone flights in recent weeks, including almost 50 on Sunday night alone, according to NJ.com, and a dismissal of them by the White House on Thursday that they were, at least mostly, “manned aircraft … being operated lawfully”.

Some of the accounts described car-sized drones, sometimes in groups, flying over sensitive military installations and critical infrastructure such as railway stations, reservoirs and power plants. In response, the Federal Aviation Administration (FAA) enacted a no-fly restriction over an army facility in Morris county and Donald Trump’s golf resort in Bedminster.

At the navy’s weapons station, ABC News reported, a spokesperson said no direct threat had been identified, but that personnel were working closely “with federal and state agencies to ensure the safety of our personnel and operations”.

The White House, Pentagon and FBI have all said they cannot fully explain the drones’ origin, but have indicated a belief they are nothing sinister.

“We have no evidence at this time that the reported drone sightings pose a national security or a public safety threat, or have a foreign nexus,” John Kirby, national security spokesperson for the Biden administration, told reporters at a press briefing on Thursday.

He said an unspecified number of still images and video footage of the incidents had been analyzed using “sophisticated electronic detection technologies” and had not been established to have involved drones.

“To the contrary, upon review of available imagery, it appears that many of the reported sightings are actually manned aircraft that are being operated lawfully,” Kirby said.

“Importantly, there are no reported or confirmed drone sightings in any restricted airspace,” he added, appearing to contradict the account of the breach at the navy weapons station.

A joint statement by the FBI and homeland security department said inquiries “have uncovered no such malicious activity or intent at this stage” in New Jersey – but noted “the reported sightings there do … highlight the insufficiency of current authorities”.

The New Jersey sightings have parallels with incidents in Europe in recent weeks also involving unidentified aircraft and military facilities. A US airbase in Ramstein, Germany, was reportedly targeted; and several “small unmanned aerial systems” were spotted last month over three British RAF bases used by the US air force.

Kirby’s comments effectively ruling out overseas involvement echoed those of Sabrina Singh, the Pentagon’s deputy press secretary, from a day earlier. “Our initial assessment here is that these are not drones or activities coming from a foreign entity or adversary,” she said.

The government’s explanation, or lack of it, has not impressed politicians, including Murphy in New Jersey, who want more action to protect citizens. The Republican representative Jeff Van Drew told the House aviation subcommittee on Wednesday that he believed the drones could be linked to Iran, and warned of a possible national security threat.

Andy Kim, the Democratic New Jersey senator, on Friday posted a video on X of what he said were several clusters of unidentified flying craft, moving erratically, low and at speed, each with flashing lights of red, green and white. He said he had filmed them on Thursday night in the company of local police – and that the objects did not show up on a regular flight tracker.

Sightings have extended well beyond New Jersey. Larry Hogan, the Republican former governor of Maryland, said in a tweet on Friday that he had “personally witnessed and videoed what appeared to be dozens of large drones” above his house in Davidsonville on Thursday night, adding the incident lasted about 45 minutes.

“Like many who have observed these drones, I do not know if this increasing activity over our skies is a threat to public safety or national security. But the public is growing increasingly concerned and frustrated with the complete lack of transparency and the dismissive attitude of the federal government,” he wrote.

“The government has the ability to track these from their point of origin but has mounted a negligent response. People are rightfully clamoring for answers, but aren’t getting any.”

Some areas of New York have also seen drone activity. In a tweet posted on Friday around lunchtime, Kathy Hochul, the state’s Democratic governor, repeated the government’s line about there being “no evidence that these drones pose a public safety or national security threat”, and said state officials were working with partners including the FBI and homeland security department “to protect New Yorkers”.

Republican New York politicians, meanwhile, were not so accepting. Vito Fossella, borough president of Staten Island, condemned the federal response at a Thursday afternoon press conference.

“What if there were 3,000 reports of drones or manned aircraft sightings over the US Capitol, or the White House, or statehouse in Albany? There would be an immediate and intense response to figure out what they were and solve the problem,” he said.

“Millions of people around here are getting nothing but: ‘Don’t believe what you see.’ The saying after 9/11 that if you see something, say something, has become: ‘If you see something, don’t worry about it.’

“The people of this city, this state and region deserve answers of what the heck is going on.”