DENVER -- Everyone has heard about the infamous Roswell incident in 1947 in New Mexico, when the government allegedly covered up the crash of an unidentified flying object. But for Colorado UFO enthusiasts, it's only the tip of the iceberg, Denver television station KMGH reported.

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Discuss: Do You Believe In UFOs?

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"It's worldwide. It goes on all the time. It has been going on since World War II. It's unabated," said John Schuessler, the international director of MUFON, or the Mutual UFO Network.

"It's a private, nonprofit group that's been around since 1969," he said of the group based in Morrison, Colo.

"Colorado is a hotbed for UFO sightings," Schuessler said.

Although MUFON is housed in Schuessler's basement, it claims to have 3,000 members worldwide with 450 field investigators.

"Wherever we hear about a UFO we go try and track it down," Schuessler said.

If it flies, hovers or spins in the sky without explanation, everyday people call MUFON.

"The calls we get are generally people who are truly mystified because something happened to them," said Schuessler.

Schuessler enjoys a little alien humor as much as the next guy, but as a retired aerospace engineer, he's dead serious about learning from the dozens of sightings he hears about each month.

"That's what I really want to see, is how these things are flying, what they do. From my very first day, the technology is what I've been interested in," said Schuessler.

Ryan Wood, of Broomfield, Colo., doesn't bother with sightings or supposed abductions. He's focused on something known as the Majestic 12.

"Majestic 12 is an organization started by President (Harry S.) Truman," Wood said. "It's a high-level team of scientists who would want to understand and deal with this extraordinary gift from the heavens, so to speak."

Wood, an energy consultant by trade, focuses on government documents that were once top secret.

"We now have thousands of pages of documents," he said.

He believes the government has a moral obligation to 'fess up about UFOs.

"It is really a crime against all humanity not to share this fact that we are not alone," Wood said.

Wood said the government may be hiding what it knows so we won't panic.

"It will be a 9/11-type event when they disclose it. History will never be the same," he said.

Wood said he's never met an informed skeptic. But those who doubt often turn to Washington aerospace journalist Philip Klass. His numerous articles over the years have debunked both UFO sightings and the Majestic 12 documents. However, that doesn't discourage Wood or the MUFON group.

And they're not alone. More than 80 million Americans believe earth has been visited by extraterrestrials.

More Information:

For more information on the Mutual UFO Network visit MUFON.com.
For more information on Ryan Wood's work and the Majestic 12 visit MajesticDocuments.com.
For more information on the Committee for the Scientific Investigation of Claims visit CSICOP.org.