A US government report on sightings of unidentified flying objects (UFOs) found no evidence of alien activity but does not rule it out, officials have told US media.
The review of 120 incidents is expected to conclude that US technology was not involved in most cases.
But beyond that, the report makes no definitive assessments about what the objects might be, officials said.
A declassified version of the report is due to be handed to lawmakers in June.
The report is the product of a military task force established last year to investigate decades of unexplained aerial sightings in US airspace.
The Department of Defense said it wanted to "improve its understanding" of unidentified aerial phenomena (UAP), also known as UFOs, and determine whether they posed a threat to national security.
The report was mandated as part of a pandemic relief package signed by former US President Donald Trump last year.
Its release has captured the imagination of the public in the US, where UFO sightings have long been the source of intrigue and alien conspiracy theories.
Speculation about the contents of the report has been building among UFO enthusiasts ahead of the its slated release to Congress on 25 June.
What do we know about the report?
Those media outlets said they spoke with multiple government officials about the findings of the highly anticipated report.
The officials said that of the 120-plus incidents documented over the past two decades, the majority were reported by US Navy personnel, while some involved foreign militaries.
CNN said it spoke with three sources who said the report does not rule out extraterrestrial activity as a possible explanation in some of these cases.
There is, however, no evidence that aerial phenomena witnessed by Navy pilots in recent years were alien spacecraft, the Times reported.
Citing intelligence officials, the newspaper said the experimental technology of a rival power, such as China or Russia, could account for at least some of the aerial phenomena.
The newspaper and CNN said intelligence officials were concerned about the national security implications of this conclusion.
What UFO incidents have been reported?
Some sightings were discussed in a recent CBS News report that renewed interest in UFOs last month.
The network's 60 Minutes programme interviewed US Navy pilots who said they had seen inexplicable aircraft that flew faster and were more manoeuvrable that anything seen before.
One retired pilot, Ryan Graves, said his fighter jet squadron began seeing UFOs hovering over restricted airspace off the coast of Virginia in 2014.
He said the objects had no visible exhaust plumes and were travelling at speeds that appeared to defy the limits of known technology.
Mr Graves said pilots training off the Atlantic Coast had similar sightings "every day for at least a couple years".
Last month Luis Elizondo, a former US counter-intelligence agent, told ABC News that some of the objects that have been sighted "can outperform anything that we have in our inventory."
"The question is, what is it?" he said. "The bottom line is, we simply don't know."
In April last year, the Department of Defense released three declassified videos of what it said showed "unexplained aerial phenomena".
The department said it wanted to "clear up any misconceptions by the public on whether or not the footage", which had already been leaked in 2007 and 2017, "was real".