A member of the Maricopa County sheriff's human-smuggling unit is on administrative leave after prosecutors last month dismissed cases against two suspects the detective arrested and vacated a verdict against another.

The detective, Alejandro Ortega, has worked for the human-smuggling unit since 2008, according to the Sheriff's Office, and investigators are examining his other arrests to determine if similar concerns have come up, said sheriff's Deputy Chief Brian Sands, who oversees the human-smuggling unit.

The cases involved a woman who was allegedly operating a drophouse out of her trailer in the 400 block of West Baseline Road in Tempe. Prosecutors made a motion to dismiss the charges in January "in the interest of justice due to the discovery of new facts in this case," according to court records.

"Our actions confirm my pledge not to proceed with defective cases," said Maricopa County Attorney Bill Montgomery, who declined to elaborate on the case beyond the reasons contained in the court records.

The human-smuggling unit is a 15-member squad established in 2007 amid concerns about undocumented immigration in the Valley and the bitter debate surrounding the issue. Since then, the unit has come under criticism from activists and scrutiny from the U.S. Justice Department, which released a report in December accusing the Sheriff's Office of instituting policies that encourage discrimination against Latino residents. Much of the report focused on the work of the human-smuggling unit and on allegations of discriminatory practices in county jails.

Sands said the office's internal investigators believe the concerns with the recently vacated and dismissed cases are limited.

"It appears that this incident is isolated to this case," Sands said. "As we progress further, we'll have to deal with other issues as they come up."

Details about what exactly led prosecutors to dismiss the cases and vacate the verdict are scant, due in part to a state law passed last year that prohibits police agencies from sharing information that may reflect negatively on officers until the officers have exhausted their appeals.

The case began in September when, according to statements Ortega wrote in a court document, an anonymous tip led the human-smuggling unit to a trailer near Baseline and Kyrene roads. When detectives arrived, they noticed two men sitting on the couch who went outside and "attempted to blend in with multiple persons attending a barbecue," according to Ortega's statement.

Detectives with the human-smuggling unit later questioned the two men, Pablo Montelongo-Martin and Aristeo Garcia-Rendon, who both said they crossed the border without authorization that morning and were waiting for a ride to Los Angeles, according to Ortega's statement.

One of the homeowners, Cecilia Margarita Serrano-Sarabia, told deputies that she picked up the men at a nearby McDonald's and was allowing them to stay at her home in exchange for financial favors from a cousin who is looking after Serrano's parents and son in Mexico, according to Ortega's statement.

Montelongo pleaded guilty to solicitation to commit human smuggling, a low-level felony, in November. Cases against the other two suspects were proceeding through court in January when an attorney for one of the defendants requested a copy of the grand-jury transcript.

That same afternoon, prosecutors filed a motion to vacate the judgment against Montelongo and dismiss the remaining charges.

Sands said that the issues surrounding this case are unique and that he doubted similar concerns would arise from Ortega's other cases.

"We're doing an inquiry; it doesn't necessarily mean anyone's guilty of an infraction, of misconduct or a crime," Sands said. "If somebody makes a mistake, you will want to look at his other work to see if there's a common denominator there. Even if it's just a simple mistake, you'll want to fix it. You don't want it to continue."