Tornadoes have touched down in northern Texas.
Local television footage shows overturned and smashed semi-trailers on the ground in the southern portion of Dallas County. Dallas Police spokeswoman Sherri Jeffrey says twisters also have caused damage in the city limits.
Weather service advisories issued Tuesday said storm spotters and radar shows separate "large and extremely dangerous" tornadoes both south of Dallas and Fort Worth.
The weather service says "considerable damage" has been reported near Cleburne, south of Fort Worth, and Lancaster, south of Dallas.
Flights were suspended at Dallas-Fort Worth Airport, and passengers were brought off planes waiting to take off.
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