Maricopa County Sheriff Joe Arpaio is facing more accusations of racial profiling stemming from his ongoing crackdown on illegal immigrants. This time, four U.S. citizens claim they were stopped and mistreated by sheriff's deputies because they are Latino.

In one case, a brother and sister say deputies unnecessarily stopped them in front of their north Phoenix auto-repair shop and forced them out of the car with weapons raised. In another, a husband and wife say sheriff's deputies improperly asked for a Social Security card after they encountered a roadblock while leaving Bartlett Lake with their two children.

The accusations were added Wednesday to a federal lawsuit that alleges the Maricopa County Sheriff's Office is targeting Latinos to investigate immigration status by using unfounded traffic stops, racially motivated questioning and baseless arrests in a series of crime sweeps.

Sheriff's officials rebutted the accusations and said the crime-suppression sweeps will continue. They have taken place in Phoenix, Guadalupe and most recently in Mesa.

"The Maricopa County Sheriff's Office does not racially profile," said Capt. Paul Chagolla, a spokesman for the office. The lawsuit "will not stop Sheriff Arpaio and the Maricopa County Sheriff's Office from doing its work enforcing all the laws, including state and federal immigration laws."

Chagolla said Arpaio was out of town and the office would not comment Wednesday about incidents described in the lawsuit.

The suit was first filed in December based on a legal immigrant's complaint that he was improperly detained by sheriff's deputies for nine hours.

The suit contends that the sweeps are a pretext for arresting illegal immigrants in violation of an agreement with U.S. Immigration and Customs Enforcement. It says sheriff's deputies are also discriminating against Latinos as part of their day-to-day operations.

"Claiming authority under a limited agreement with U.S. Immigration and Customs Enforcement that actually prohibits the practices challenged here, (Arpaio and the Maricopa County Sheriff's Office) have launched a series of massive so-called 'crime suppression sweeps' that show a law enforcement agency operating well beyond the bounds of the law," the suit says.

Vincent Picard, a spokesman for ICE, said the Sheriff's Office has not violated the agreement. The agreement allows up to 160 specially trained sheriff's deputies and jail officers to enforce federal immigration laws.

The accusations filed on Wednesday attempt to add muscle to the existing lawsuit and involve U.S. citizens. On Dec. 2, according to the lawsuit, David and Jessica Rodriguez were leaving Bartlett Lake with their two young children when deputies pulled them over after they encountered a washed-out area of road and made a U-turn.

The suit says deputies asked David Rodriguez for a Social Security card, driver's license, vehicle registration and proof of insurance but did not ask for documentation from other drivers who had also driven down the same closed road.

When Jessica Rodriguez asked why the deputy needed to see a Social Security card, the deputy responded, "standard procedure," the suit says.

The suit says David Rodriguez was cited for failure to obey a traffic-control device while other drivers who were White got warnings.

On March 28, Velia Meraz and her brother, Manuel Nieto Jr., said they were mistreated by sheriff's deputies in front of their family's business, Manuel's Auto Repair, on Cave Creek Road near East Nisbet Road. Sheriff's deputies were conducting a crime sweep not far from the family's business.

The sister and brother said they had just come from a nearby convenience store where they saw a sheriff's deputy talking to two Latino-looking men in handcuffs.

The officer yelled at them to leave, and when Meraz asked why, the deputy threatened to arrest them for disorderly conduct, the lawsuit says. When Meraz and Nieto drove to the auto-repair shop 50 yards away, four police vehicles descended on them, blocking the street and the business, the suit says. The officers jumped out of their vehicles with their weapons raised, and Nieto was pulled out of his car and pressed face first against his car, and handcuffed.

The officers let Nieto go after running his driver's license information through a computer. He was not cited.

Meraz said she and her brother were born in Chicago and moved to Arizona 17 years ago.

"I was very upset," she said. "I can't even put into words how I felt."

"What he is doing is overstepping the line. It's not right," Meraz added about Arpaio.

The incident in the December lawsuit involved Mexican immigrant Manuel de Jesus Ortega Melendres.

On Sept. 26, Ortega, who was in the country legally, said he was passenger in a vehicle driven by a White driver stopped by sheriff's deputies in Cave Creek. Ortega said deputies detained him for nine hours.

The lawsuit is the latest legal salvo by civil liberties and Latino groups trying to prove Arpaio is using racial profiling to arrest illegal immigrants. The suit is supported by the American Civil Liberties Union, the ACLU of Arizona and the Mexican American Legal Defense and Educational Fund. The lead attorney is David Bodney of the Phoenix firm Steptoe & Johnson. Bodney also represents The Arizona Republic on First Amendment issues.

Proving racial profiling is a difficult task. Federal courts have repeatedly ruled that police cannot target someone to investigate based on race because it violates equal-protection rights under the U.S. Constitution and the 1964 civil-rights act.

But proving the discrimination was intentional, as required, has become harder in the wake of the 9/11 terrorist attacks because of concerns over limiting law enforcement's ability to apprehend terrorists.