The Chilean navy has released a nine-minute video of a UFO flying over the country's coast near Santiago, admitting it has no idea what it could be.
The footage was shot in 2014 from a helicopter by a navy technician testing a new infrared camera, reports the Huffington Post.
The mysterious object could be seen with the naked eye, but couldn't be detected by the helicopter's radar, ground radar stations or air traffic controllers. No aircraft had been authorised to fly in the area.
In the nine-minute video, the UFO twice emits "some type of gas or liquid with a high thermal track or signal", the technician told the Huffington Post.
Chilean officials spent two years investigating the footage, and came up empty.
One suggestion was that it was an aircraft dumping waste water, which officials ruled out because it wasn't on radar, nor cleared to land.
And at that altitude - only 4,500 feet (1400m) - water would have plummeted to the ground, not formed the plumes that can be seen in the video.
The object's appearance on infra-red camera suggests it could be a drone, but again, didn't show up on radar, and no drones were registered.
Another suggestion was space debris, perhaps releasing compressed gas. This was ruled out because it was flying horizontally, and appeared to be under control and not at the mercy of the wind.
Computer alteration of the footage was also ruled out, also the possibility it could have been a hang gilder, parachute, balloon, bird or insect.
"It can be concluded that the object has all the characteristics to be classified as an unidentified aerial phenomenon," said Alberto Vergara, lead analyst from the Chilean Air Force's photogrammetric department.
The investigation was carried out by the Comité de Estudios de Fenómenos Aéreos Anómalos, an agency set up in the 1990s at the height of the craze over TV show The X-Files, tasked with investigating anomalous phenomena.