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The police chief in Fort Worth, Texas, is apologizing after allowing his officers to take part in a federal survey in which random drivers were pulled over and asked to submit breath, saliva and even blood samples.

Fort Worth police set up checkpoints on city streets, and ordered random motorists off the road as part of a nationwide federal survey of alcohol- and drug-impaired driving last week, according to The Star-Telegram. The drivers were asked to pull into a parking lot, where they could give a cheek swab and volunteer for a blood or breath test. Those who agreed were paid $10 to $50. Those who declined were briefly interviewed and allowed to leave.

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Some drivers complained of feeling strong-armed into participating, and on Wednesday, Police Chief Jeffrey Halstead apologized.

"We realize this survey caused many of our citizens frustration and we apologize for our participation," Halstead said in a statement. "I agree with our citizens' concerns and I apologize for our participation. "Any future federal survey of this nature, which jeopardizes the public's trust, will not be approved for the use of Fort Worth police."

The survey was conducted by the National Highway Traffic Safety Administration. The survey is done every 10 years or so and was reportedly intended to determine the prevalence of alcohol and drug use by drivers. Checkpoints to collect samples have been set up in 30 cities nationwide, and samples remain anonymous, according to federal officials. But law enforcement agencies in other jurisdictions have taken measures to ensure that motorists know it is a "paid volunteer survey," and that they do not have to pull over.

Carl Olund, one driver who was pulled over in Fort Worth, told NBCDFW.com he felt pressured to provide samples of his breath and saliva to the federal workers there. He said he was not told it was voluntary.

"But she was like up in my window to where I was like, 'OK, I might as well just stay.' I mean, the cops are around, so if I take off, I'm not going to have four or five cops chasing me."

An internal review at the department is under way.

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