"Last night's storms led to widespread damage throughout a large portion of the state," Fallin said in a statement. "I appreciate the ongoing work of our first responders who have been working through the night to assist those in need."
Storms destroyed buildings, tore off roofs and ravaged a mobile home park in a suburb of Tulsa, according to the Tulsa County Sheriff's Office.
Some 80,000 Oklahoma residents were left without power Wednesday evening, the Oklahoma Department of Emergency Management said. By Thursday morning, that number dropped to about 15,000, according to department spokeswoman Keli Cain.
Tornadoes hit throughout the state, as well as in Arkansas. One small tornado swept through the suburb of Moore in Oklahoma City, Cain said, where 24 people died in a tornado in 2013.