Locals in Portugal were left baffled after mysterious strands of wispy, white "angel hair" were filmed raining from the sky over the weekend, UK Metro reported.

As the substance "came alive" under ultraviolet light, UFO enthusiasts were left questioning whether the sparkling sight was the work of terrestrial origin or had been created by a passing UFO.

"It fell during the afternoon. I tried to inquire if airplanes flew over before, but no straight answer. It happened two weekends in a row," one local, who did not want to be identified, told the Metro.

"Me and a couple of friends sent it to be analyzed - and the weirdest things happened. It reacts to UV light. It comes alive."

Angel hair, like a cobweb or a jelly, has been described to be a sticky, fibrous substance related in connection with UFO sightings, or manifestations of the Virgin Mary, according to Wikipedia.

Conspiracy theorists claim "that it disintegrates or evaporates within a short time of forming, according to AOL.com. "Angel hair is also an important aspect of the UFO religion Raëlism, and one theory among ufologists is that it is created from 'ionized air sleeting off an electromagnetic field' that surrounds a UFO."

Additionally, other "scientific explanations suggest that it's an atmospheric natural phenomenon, or caused by spiders. Atmospheric electricity may also cause floating dust particles to become polarized, and attraction between these polarized dust particles may cause them to join together, to form long filaments."

Nigel Watson, author of the Haynes Manual for UFO Investigations, said, "Sightings of UFOs were commonly associated with angel hair up to the 1970s, and in the past it has been seen in association with religious visions in the sky, such as in Fatima, Portugal in 1917."

"These fine fibers falling from the sky were regarded as being the byproduct of UFO propulsion systems, although skeptics tend to explain them as being created by migrating spiders or by dust particles polarized by atmospheric electricity and are a natural phenomenon."

"It is only in recent years that angel hair sightings have returned again. Samples quickly evaporate making it difficult to analyze their composition and nature," he added.

Meanwhile, countries such as Finland and Canada have reported similar sightings of strands falling from the sky. But since the samples are known to evaporate quickly, they haven't been properly examined.