FACTBOX: Recent events in U.S. coal mine safety

(Reuters) - A cave-in at a Utah coal mine that killed three rescue workers, who were looking for miners who have been trapped underground, is one in a string of industry incidents that started in 2006, the deadliest year for coal mining in a decade.

Rescuers suspended efforts on Friday to build a tunnel to search for the six miners who have been trapped since August 6. Please click for story.

Last year, an explosion at the West Virginia Sago Mine killed 12 miners and prompted Congress to pass new safety laws for the industry. That year, 48 miners died in accidents.

From 1997 to 2006, an average of nearly 33 coal miners died annually in accidents. So far this year, not counting the Utah rescue workers, 14 miners have died.

Fewer annual accidents happen now than during the first half of the last century when coal fueled America's great industrial growth, and it was common for accidents to kill more than 100 miners. The industry employs far fewer workers now.

Here is a list of recent events in U.S. coal mine safety:

2007

--July: Coal mining company Massey Energy said new federal mine safety rules, inspired by the Sago disaster, could cost the company $24 million adding 50 to 75 cents per ton to the cost of its coal.

--August 6: Six miners were trapped underground at the Crandall Canyon Mine in Utah after a collapse of such force geologists are investigating whether it accounted for an earthquake registered at the same time. Private company Murray Energy owns the mine operator. The U.S. Mine Safety and Health Administration said the mine was engaged in "retreat mining" in which pillars of coal supporting the roof are mined allowing the shaft to collapse.

2006

--January 2: An underground explosion killed 12 miners International Coal Group's Sago mine in West Virginia after an underground explosion. Another accident in the state within three weeks of Sago killed two other miners.

--May 20: An underground explosion killed five miners at Kentucky Darby LLC mine.

--Summer: Prompted by Sago, Congress passed the Miner Act of 2006 and President George W.Bush signed it into law. It was the first major revision to U.S. mine safety laws since 1977. It requires mines to:

-Provide more emergency supplies of breathable air along escape routes

-Make available two rescue teams capable of a one-hour response time

-Provide wireless two-way communications and electronic tracking systems for miners within three years.