Several Navy officers who witnessed the now-famous Nimitz UFO encounter in 2004 say "unknown individuals" showed up after the event and made them turn over data recordings and videos, according to Popular Mechanics .

For several days in November 2004, a Navy missile cruiser sailing around 100 miles (160 kilometers) off the coast of southern California detected strange radar signals emanating from an object in the sky. The signals were erratic and didn't seem to match those given off by known aircraft. The Navy then deployed fighter jets to catch a closer glimpse of the strange object, and one succeeded in recording a blurry, black-and-white video that was, to the government's chagrin, publicly released in 2017 along with two other videos of UFO sightings from years later.

Five Navy veterans recently spoke to Popular Mechanics about what they experienced at the time. The veterans were part of the Navy's Strike Carrier Group 11 and were sailing on the USS Princeton on a training mission prior to their upcoming deployment in the Arabian Sea.

Related: 7 Things Most Often Mistaken for UFOs

The strange radar signals came from an object that would quickly change altitudes, sometimes lurking at 80,000 feet (24,000 meters) and other times hanging around at 30,000 feet (9,000 m), they told Popular Mechanics. The UFO (an "unidentified flying object," which doesn't necessarily belong to aliens ) became known as "Tic Tac" because of its shape. Tic Tac gave off a phosphorus glow at night and would dart around in various directions, said one of the veterans, Gary Voorhis, who looked at the object through binoculars on the ship.

Voorhis recalled that sometime after the officers recorded these strange radio signals, two people showed up on a helicopter, and 20 minutes later, Voorhis' chain of command (a higher-up authority figure) told him to turn over the data recordings. His chain of command also told him to delete the recordings on the ship. "They even told me to erase everything that's in the shop — even the blank tapes," he told Popular Mechanics.

Similarly, Petty Officer Patrick "P.J." Hughes, who was an aviation technician, claimed that his commanding officer and two unknown men asked him to turn over the hard drives from the plane.

However, Cmdr. David Fravor, one of the pilots who got a close view of Tic Tac on a fighter jet, told a different story. In various past interviews, Fravor said the videotapes of the UFO disappeared — not because of any "men in suits" but because people had unintentionally recorded over them.

Fravor previously told The New York Times that he and Lt. Cmdr. Jim Slaight spotted the object, which was about 40 feet (12 m) long. As they descended in the fighter jet, the object ascended to meet them but then abruptly veered away and disappeared , he told the Times.

The details of what happened in 2004, both in the sky and down below, remain ambiguous. To learn more about what these Navy witnesses had to say, read Popular Mechanics' original feature .

Originally published on Live Science .