The coal miner faces citations for a May 1 detonation near the Wyoming town of Gillette which US Geological Survey seismographs measured at 4.5 on the Richter scale.

Citations for state and federal blasting violations are reportedly being pursued by the Wyoming Department of Environmental Quality and the Mine Safety and Health Administration.

State government notices issued to Cloud Peak described the blast as three times its intended size.

The Wyoming Casper Star Tribune newspaper said the mine expected to set off 26,852 pounds of explosives but accidentally triggered adjacent explosives creating a blast in excess of the legal limit of 85,308 pounds of explosives.

Cloud Peak officials have not released a public statement on any events at the complex though the blasters in charge of the explosion have been suspended by the state for at least 60 days.

Local media reported the surface miner had not yet been fined but would be required to submit plans showing the steps it would take to prevent a repeat incident.

The Cordero Rojo operation, which extracts from the Wyodak seam at a seam thickness range of 55 to 70 feet, mined and shipped about 39.5 million tons of low-sulfur coal last year.

Wyoming’s Powder River Basin mines produced 426Mt of coal in 2011.