(CNN) -- Emergency officials in seven Mississippi counties were dealing Monday with widespread damage after a swarm of storms swept through the area Sunday evening, injuring at least 16 people.
No deaths have been reported.
Two people in Lamar County were critically hurt, the Mississippi Emergency Management Agency said.
A tornado struck Hattiesburg, a southern Mississippi city that straddles Lamar and Forrest counties.
Hattiesburg Mayor Johnny DuPree reported major damage to a number of structures. "If there is a good thing about this, it happened on a Sunday when most of these structures were vacant," he said.
Several homes were destroyed in Marion County, and numerous structures -- including businesses and public buildings -- sustained "significant damage," the state emergency management agency said.
As of Monday morning, 4,000 power customers were without electricity, down from the approximately 14,000 who had lost power, Mississippi Power spokesman Mark Davis said.
Mississippi Gov. Phil Bryant declared a state of emergency for the affected counties. The declaration means state resources and assets can be used to support local response efforts.
Bryant tweeted photos of the storm damage.
In Hattiesburg, the University of Southern Mississippi suffered damage to several buildings, but there were no reports of injuries there.
University police declared a state of emergency and urged those not on campus to stay away until further notice.
Nearby Oak Grove High School also suffered damage. Randy Wright posted photographs to his Twitter account, showing debris strewn on what appeared to be a parking lot and a truck upside down in a baseball diamond.
The Hattiesburg Public School District canceled classes Monday. The university campus will also be closed.
"There's quite a few homes without power at this point," Forrest County Sheriff Billy McGee said. "Quite a few trees on houses, on cars, that type of thing."
Ten to 15 people were hospitalized, but none suffered serious injuries, he said.
It was not clear how those people were hurt.
Sarah Lawrence, a Hattiesburg resident, said that the storm sounded like "stuff being thrown."
"Within seconds, everything changed," she said. "I didn't feel like there was much notice. I heard the sirens and everything looked OK outside, so I started making preparations to go into the bathroom. And then, next thing I know, all the lights went out, and it got dark outside."
CNN's Maggie Schneider, Chandler Friedman, Elwyn Lopez and Janet DiGiacomo contributed to this report.