Houston —  Multiple tornadoes ripped through the Dallas-Fort Worth area Tuesday, with two major twisters damaging hundreds of homes and causing numerous injuries, some critical.

The mayor of Lancaster, Texas, a suburb about 15 miles south of Dallas, saw one of the twisters approach.

“I was leaving a meeting here in town and heard the tornado sirens go off,” said Mayor Marcus Knight at a news conference, adding that he watched the tornado bear down on the area before arriving at City Hall.

PHOTOS: Texas tornadoes

After the tornado struck, Knight said multiple injuries were reported, sending some victims to the hospital. No fatalities were reported, he said.

At least 300 structures were damaged, half of them severely, he said.

The city was declared a disaster area and its recreation center was converted into a shelter. Dallas County sheriff’s deputies responded to reports of looting, and Dallas Sheriff Lupe Valdez toured the area, a spokeswoman said.

A curfew was imposed overnight and part of the city blockaded, Knight said.

“The public’s safety is paramount,” he said.

About 30 miles northwest, a tornado tore through Arlington, home of the Texas Rangers, causing significant damage to homes and businesses and leading that city’s mayor to sign a disaster declaration.

About 25 miles west in Burleson, Spinks Airport manager Aaron Barth also spotted a tornado approaching from a distance shortly before 1 p.m. Tuesday.

“The rotation was present there and slowly descended down, touched down for about 15 seconds one to two miles east,” he said.

As he watched, the twister veered away from the airport, causing no injuries or damage, Barth said.

Elsewhere, the tornadoes tossed tractor-trailers, ripped the roofs off houses, churned walls into planks and strewed them across suburban streets.

Emergency responders were still trying to tally damages late Tuesday.

“I can’t give damage assessment numbers because the storm system is so broad based, it’s covering such a wide swath of the region,” said Maria Anita, a Dallas County spokeswoman.

At least 12,000 people were without power in Fort Worth after the tornadoes hit, a Tarrant County spokesman said.

In addition to tornadoes, the area was hit with thunderstorms that dumped damaging hail the size of baseballs in places.

American Airlines canceled nearly all departures from its hub at Dallas-Fort Worth International Airport on Tuesday evening and diverted others to different airports, according to Fort Worth-based spokesman Tim Smith. Smith said the airline also pulled almost 100 planes to inspect for hail damage as required by the Federal Aviation Administration after the storms dropped hail ranging from pea to golf-ball size.

At Dallas Love Field, passengers were forced to evacuate and take temporary shelter during the storm, and late Tuesday, Southwest canceled more than 45 flights.

Gov. Rick Perry issued a statement noting that the state operations center in San Antonio has been activated to assist with the emergency response and urging North Texas residents in hard-hit areas to stay off the roads and allow first responders to do their jobs.

A tornado watch remained in effect late Tuesday for 10 counties in north and central Texas.

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molly.hennessy-fiske@latimes.com