The U.S. Justice Department announced Friday that it would send federal observers to Farmers Branch and Irving to ensure compliance with the Voting Rights Act during today's municipal elections.

A Justice spokesman wouldn't say what prompted the action.

While illegal immigration has stirred emotions in both cities, Irving Mayor Herbert Gears said he had heard of no special monitoring taking place specifically because of the issue.

"It's not uncommon for them to monitor our elections," Mr. Gears said. "We have an at-large elections system, and there's currently a lawsuit over single-member districts, so they've monitored us before."

Farmers Branch also has been sued because of its at-large election system, as well as measures to ban housing rentals to illegal immigrants.

Farmers Branch Mayor Bob Phelps said the Justice Department's decision could be related to any of the lawsuits over single-member districts or illegal immigration that the city is facing.

Federal monitors also were on hand last May, when the city's voters overwhelmingly approved a ban on renting apartments to illegal immigrants.

Emotions have been running high in both cities in advance of today's election, and illegal immigration has been a key issue in the races for mayor and city council in both cities.

The Dallas County Elections Department has predicted voter turnout of about 35 percent in Farmers Branch and 15 to 20 percent in Irving.