A 5.6 magnitude earthquake struck Saturday morning near Pawnee, Oklahoma, and rattled through at least six surrounding states in the US heartland, according to the US Geological Survey. The earthquake was also felt in Kansas, Arkansas, Missouri, Texas, Nebraska, and Iowa, according to the USGS. The Oklahoma Corporation Commission, a regulatory agency that examines the state's fuel, oil, gas, public utilities and transportation industries, is "reviewing disposal wells in the vicinity of the earthquake near Pawnee," Oklahoma Gov. Mary Fallin said via Twitter.