An investigation by the United Stats government of 144 UFO sightings yielded nothing conclusive.

This, as a long-awaited U.S. government report on UFOs released Friday made at least one thing clear: The truth is still out there.

Investigators did not find extraterrestrial links in reviewing 144 sightings of aircraft or other devices apparently flying at mysterious speeds or trajectories. But they drew few other conclusions and instead highlighted the need for better data collection about what’s increasingly seen by Democrats and Republicans as a national security concern. In all but one of the sightings investigated, there was too little information for investigators to even broadly characterize the nature of the incident.

There were 18 cases in which witnesses saw “unusual” patterns of movement or flight characteristics, the report said, adding that more analysis was needed to determine if those sightings represented “breakthrough” technology.

Long the domain of science fiction and so-called ufologists, the subject of UFOs has in recent years drawn serious study from the Pentagon and intelligence agencies. The prospect of an adversary spying with unknown technology has alarmed lawmakers in both parties.

Congress last year required the creation of the report delivered Friday. While its lack of conclusions has already been made public, the report on what the government calls “unidentified aerial phenomena” still represents a milestone in the study of the issue.

U.S. officials who briefed reporters on condition of anonymity said there were “no clear indications” that the sightings could be linked to alien life. There is also no definitive linkage of sightings to potentially unknown technology of an adversary like Russia or China.

“It’s clear that we need to improve our capacity to further analyze remaining UAP observations, even as we accept that there are some limits to our capacity to characterize and understand some of the observations that we have,” one official said.

The report was published online and delivered to the House and Senate intelligence committees with a classified annex. Lawmakers were given a briefing last week on the investigation. One person who attended the classified briefing and spoke on condition of anonymity said that lawmakers were given little information beyond what’s publicly available and that the only videos shown had already been made public.

The report lists five potential categories, including the possibility of foreign adversaries flying unknown technology to events occurring naturally in the atmosphere.

But only one instance was categorized as “airborne clutter” and believed to be a large, deflating balloon. The rest are uncategorized because of a lack of information. That includes three instances of potential sightings captured on videos that were declassified and released in recent years.