A funnel cloud is seen in the Dallas area.
The service tweeted it had visual confirmation north of Interstate 635 and east of I-75 around 9:30 p.m. CDT.
Three people were transported to local hospitals with storm-related injuries that were not life-threatening, according to the City of Dallas Office of Emergency Management.
Emergency services are checking for any victims amid fallen trees, torn roofs, downed power lines and damaged cars.
Oncor said early Monday that there's no estimated time of restoration.
The Dallas metro area now has over 94,000 customers without power, according to the electric company Oncor.More news: Reliance Jio marginally cuts mid-value tariff packs, adjusts IUC
The Mayor of Dallas Eric Johnson said the city was "preparing to open Bachman Recreation Center" for people seeking shelter in the aftermath of the Texas storm, later adding that the Red Cross would be on site. A second set of teams will resume search efforts in daylight. The Dallas Morning News reports that tens of thousands of people were left without power.
Evans said the department had also received multiple calls from people injured in their homes by broken glass.
The KNON-FM radio station went off the air as its studio suffered major damage. He told the host of the show that had been broadcasting to follow him to the bathroom, to get away from all the glass.
Godwin says the size and severity of the tornado won't be known until crews arrive to survey the damage.
All tornado warnings have been lifted and there are no flash flood warnings, it added.More news: John Mulaney Makes 'Dickinson' Debut In Hailee Steinfeld-Starring Show's New Trailer
Meanwhile, the line of storms responsible for the tornado threatened parts of the Plains with more severe weather.
North of Dallas, the city of Richardson said in a release that thoroughfares "used by thousands of morning commuters" will be closed while workers clear debris and fix downed traffic lights.
According to Oncor, almost 112,000 customers are affected by power outages. A line of storms was moving east-southeast at 50 to 55 miles per hour Monday morning, the weather service said. Four homes were left uninhabitable, but no injuries had been reported.
A number of schools in the north-west of Dallas have cancelled classes after suffering extensive damage to campuses.
© Provided by The Associated Press This Oct. 20, 2019 image made from video by Twitter user @AthenaRising shows the tornado in Rockwall, TX.More news: Twitter's Android app gets OLED-friendly dark mode in new alpha build