Three weeks after the cave-in of the Crandall Canyon Mine, rescuers are still searching for missing miners, but now they're hoping for help from a robotic camera. After drilling another hole into the mine, and finding no new information, rescuers were planning to use an 8-inch, 70-pound, waterproof camera to search for possible survivors.

The robot, constructed over the past week by the Canadian company Inuktun, could be lowered up to 2,000 feet, and should then be able to travel another 1,000 on its own. It has two cameras and a 200-watt light to brighten up the space, but there's no guarantee that it will even make it down into the holes.—Gregory Mone

When six men got trapped in a Utah coal mine on August 6, the mine's chief executive declared that the cave-in was caused by a natural earthquake. The University of Utah Seismograph Stations did record a magnitude-3.9 earthquake, but the quake was probably caused by the mine collapse—rather than the other way around.

Seismograph stations recorded a smaller seismic event on Thursday, when a second implosion killed three men who were participating in the rescue effort, including an inspector from the U.S. Labor Department's Mine Safety and Health Administration. Called a "bump" by mining officials, it is the seismic event recorded in blue on the lower right section of this chart.

Seismologists at the University of Utah, the U.S. Geological Survey and the University of California, Berkeley, say that the downward motion of seismic waves from both events is strong evidence of collapse. The second event happened less than a mile underground, which would be quite shallow for a natural earthquake.

The "bumps" are likely to continue. The roof of the Crandall Canyon mine is held up by pillars of coal. When some pillars fail, that can increase the stress on nearby pillars that are still standing.—Dawn Stover

This week's tragic coal-mine collapse in Utah has become the focus of an argument between scientists studying the event and executives at Murray Energy Corp., the company that owns the Crandall Canyon mine. On Monday, University of Utah seismographs recorded shaking near the mine that registered 3.9 on the Richter Scale, and 10 smaller aftershocks over the next day.

The company says the initial quake is what caved in the mine, but seismologists are arguing that the data suggests it was the other way around. They contend that a natural earthquake has a different seismic signature than the shaking produced by a cave-in, and that the data they picked up is more consistent with the latter scenario. Murray Energy, meanwhile, insists that the event was a natural disaster, and that they can prove it. —Gregory Mone

Via AP