In the days following reports that a solar observatory in New Mexico had been abruptly evacuated and closed with FBI agents on the scene, the internet exploded with theories.

Aliens? UFOs? Some other mysterious extraterrestrial encounter?

Questions outnumbered answers as the National Solar Observatory in Sunspot, N.M., stayed shuttered for 10 days earlier this month, its entrance roped off with crime-scene tape and guarded by security personnel. Federal authorities remained tight-lipped, which only fueled speculation and frustrated local law enforcement, who were also kept in the dark.

On Monday, the facility reopened, and for the first time in more than a week there was finally a sliver of information about what had caused the sudden closure. The Association of Universities for Research in Astronomy, which manages the observatory and its surrounding buildings, said in a statement that it had been cooperating with an “ongoing law enforcement investigation of criminal activity” at the site. There was no additional information, and both federal and local agencies declined to provide any details.

But, much to the disappointment of conspiracy theorists, what appears to have triggered the observatory’s complete shutdown was a janitor who had allegedly been using the observatory’s Wi-Fi to download and distribute child pornography, according to newly unsealed court documents.

In July, FBI agents investigating child sexual exploitation traced the location of several IP addresses linked to child pornography activity to the observatory, according to a 39-page search warrant application.

During an interview with federal authorities on Aug. 21, the facility’s chief observer said he had found, on a number of occasions, the same laptop hidden and running in various seldom-used offices around the observatory. He described the contents of the laptop as “not good,” according to court documents.

A federal agent immediately went to the observatory, located deep within Lincoln National Forest, and took the laptop into evidence.

According to the warrant application, the only person in the facility at the same time the alleged child porn downloads occurred was a janitor who had started work there about a year ago. The observatory’s cleaning contract was owned by the janitor’s parents, authorities said.

“[The janitor] has a key to the building and unlimited access to the building, and is familiar with which offices are used only a handful of times a year,” the warrant application said. The application included the name of the janitor but because he has not been charged with anything at this time, the Post is not identifying him.

The day after the laptop was seized, the janitor was allegedly seen by the chief observer leaving the office where it had been found. The janitor asked the chief observer, who relayed the interaction to federal agents, if anyone else had entered the office because the cleaning supplies he had left there were missing. Later, the janitor claimed “someone had been entering the Observatory at night, in order to steal the wireless internet service,” and expressed concerns about “lax security,” court documents reported.

Then, the janitor’s actions allegedly became even more bizarre, prompting the observatory’s staff to become worried about their own safety. At one point, he was described as “frantic,” authorities said.

Aside from continuing to “feverishly” search the facility, the documents state that the janitor said, “it was only a matter of time before the facility ‘got hit,’ ” and that he “believed there was a serial killer in the area, and that he was fearful that the killer might enter the facility and execute someone.”

In response to the janitor’s behavior, the management of the observatory, without input from the FBI, shut it down and evacuated its personnel. The facility’s cleaning contract with the janitor’s parents was also terminated.

The FBI obtained a warrant to search the janitor’s home and on Sept. 14, federal agents seized cellphones and laptops, and storage devices including SD cards, thumb drives and an external hard drive, court documents said.

No charges have been filed and an arrest warrant for the man has not been issued, Reuters reported. An FBI spokesperson told Reuters the case is still under investigation.