Members of Congress continue to demand answers on mysterious drone activity on the East Coast that has alarmed residents and officials, with several senators expressing "urgent concern," as the White House downplayed concerns over some of the sightings.

National security adviser John Kirby said that the White House hasn't been able to corroborate ‘any of the reported (drone) sightings.'

There is no evidence to show that recent drone sightings over New Jersey pose a national security or public safety risk, federal security officials and the White House said.