A very bright, loud meteor streaked over Custer County airspace early Monday morning. Two miners saw a large fireball light up the Squaw Creek drainage as bright as day, then break up into half a dozen smaller pieces and fizzle out.

The sonic boom woke sleepers and lit the skies from the Pahsimeroi, Challis and Clayton, to Stanley. The meteor was spotted from Pine and Featherville, to Boise and McCall.

Dispatcher Traudy Dunkle was on duty at the Custer County Sheriff's Office and reported what sounded like a sonic boom about 4:45 a.m. She received multiple 911 calls about rumbling and shaking of buildings, bright lights and explosions. Some callers weren't sure whether it was an airplane exploding, a meteor or an earthquake.

Thompson Creek Mine employees Robert Fisher and Dave Hewitt were carpooling on their way to work when they saw a huge, glowing red fireball with a vapor trail that lit up the sky with an intense blue light.

"It lit up everything," Fisher said. "You could see almost like it was daylight."

The fireball was flying from north to south, he said, parallel to their vehicle as they drove up Squaw Creek. They slammed on the brakes.

The meteor was fairly low on the horizon, said Fisher. The two didn't hear the sonic boom that others heard, but they saw the fireball burst into 5-7 chunks, producing other colors in the yellow to orange range. The smaller pieces then fizzled out like spent fireworks.

"It was spectacular," Fisher said. "It went out all at once. We were expecting an impact," Fisher added, but he and Hewitt didn't hear one. "It lit up the whole canyon," Hewitt said. The whole experience lasted about 10 seconds.

Up at the mine, other employees felt buildings shake and some thought the mill had exploded. They reported to the sheriff's office that it looked like the meteor broke up over Potaman Peak south of Clayton.

"You're lucky to see something like that once in a lifetime," Fisher said.

Fisher and Hewitt said it was hard to estimate the meteor's size, but the light was so intense it might have been as big as a school bus, with smaller pieces the size of refrigerators or basketballs.

"It was huge," Hewitt said, and flying low to the horizon. Both thought it was big enough to be tracked on radar.

As many as 15-20 Thompson Creek employees saw the meteor while commuting to work, including Don Rowles and Frank Robinson, who also saw the intense whitish blue light that lit up the whole Salmon River canyon.

"I thought it was a spaceship and I was going to be beamed up," Rowles joked.

The Challis Messenger called around to check, touching base with state and federal agencies from NORAD to NASA.

Michael Stickney, director of earthquake studies at the Montana Bureau of Mines and Geology, said his seismograph network didn't record any earthquakes in our area Monday morning. The closest instrument that could register a sonic boom, at Clark Canyon Reservoir, didn't record any data, Stickney said.

The Bruneau Dunes Observatory, in Bruneau Dunes State Park, offered more information.

Observatory operator and state park employee Bob Niemeyer, said sonic booms are only heard within 50 miles of meteors as they enter the lower atmosphere, so based on citizen reports, Custer County was closest.

The reports from Pine, Featherville and Boise were all about 4:44 a.m., so everyone probably saw the same meteor, Niemeyer said.

Size can be deceiving. A meteor the size of a walnut can light up the sky brighter than the moon. "Small ones can be spectacular," he said. The fact that the meteor broke up into smaller pieces in mid-air, probably means no chunks of debris fell to earth. Splitting or exploding meteors are called bolides, said Niemeyer.

There were no reports of the Federal Aviation Adminis-tration tracking the meteor on radar from towers in Boise and Mountain Home, Niemeyer said.

The Custer County meteor was no doubt a "background" meteor, he said, meaning it's not part of a meteor shower associated with debris from comets orbiting the sun, but rather one from the asteroid belt or left over from the early formation of the solar system.

Meteor showers, produced by cometary debris, occur annually as the earth's orbit takes it through the path of the old comet. Debris is typically small dust ? or sand grain ? sized particles, Niemeyer said.

Debris from perhaps the most famous comet, Halley's, produces two meteor showers per year, the Eta Aquarids in May and the Oronids in October. The 2007 meteor shower calendar on the American Meteor Society's website, shows we are in- between the June Lyrid and Bootid meteor showers.

The plasma, or ionized gas trail, from a glowing red fireball can produce a blue light and indicates the meteor is primarily made of nickel and iron, according to Niemeyer, with traces of iridium possible.