A national solar observatory in Sunspot, New Mexico is at the centre of an FBI investigation, prompting a frenzy of conspiracy theories.
The observatory has been closed since last Thursday, when it was suddenly evacuated by FBI officials tasked with investigating an undisclosed "security issue".
Government officials have refused to elaborate on what is behind the unexpected closure.
The silence from officials has set off a range of theories, including a possible alien sighting, unexpected movement in the sun or a mercury leak.
Along with the Sunspot Solar Observatory, a local post office and around a dozen residents have been evacuated.
Local county sheriff Benny House described blackhawk helicopters circling the area, as well as military figures working with antennas.
Mr House said that the FBI has kept local residents in the dark, adding: "The FBI is refusing to tell us what’s going on.
"What their purpose was nobody will say. But for the FBI to get involved that quick and be so secretive about it, there was a lot of stuff going on up there.
"There was a Blackhawk helicopter, a bunch of people around antennas and work crews on towers but nobody would tell us anything."
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