The tornado caused "heavy damage" in Van, Smith County Emergency Management spokesman Keith Tate said. Van is a city of 2,600 people about 73 miles east of Dallas.
"Damages range from completely destroyed homes, damaged homes, to trees and power lines down," added Chuck Allen, emergency management coordinator for Van Zandt County.
Emergency workers spent early Monday going door to door in search of other victims.
"Once we get daylight, we will be able to identify areas that are affected and lead responders in to verify the [houses] are clear of any individuals needing medical attention," Allen said.
The American Red Cross was also on the scene and establishing a shelter in a local church.
The severe weather struck around 8:45 p.m. local time (9:45 p.m. ET). It was one of at least 26 tornadoes reported across the U.S. on Sunday.
The area also saw heavy rains and widespread flash flooding. Two groups of people had to be airlifted to safety on Sunday, authorities in Denton County said.
More than 5 inches of rain fell in Navarro City in just a few hours, prompting a flash flood emergency, NBC Dallas-Fort Worth reported.
Van, Texas, Hit by Tornado; Homes `Completely Destroyed`, 26 Hurt - VIDEO
11 May 2015
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At least 26 people were hospitalized when a tornado ripped through East Texas on Sunday, damaging about 30 percent of a city, authorities said.
