SIOUX FALLS, S.D. (AP) – The American Civil Liberties Union is investigating whether the South Dakota Department of Social Services violated federal law by removing Native American children from their homes and placing them in foster care instead of with relatives.

Tate Walker, an ACLU spokeswoman in Sioux Falls, said the civil rights organization has fielded individual complaints for years from families who said the state violated the federal Indian Child Welfare Act. The law directs officials to place Native American children removed from homes with their relatives or tribes except in unusual situations.

But the cases had been too scattered and disparate to tackle, Walker said, until a recent National Public Radio series accused the state of routinely breaking the law and disrupting the lives of hundreds of Native Americans each year.

“That aired and then boom: We're getting calls left and right,” Walker told The Associated Press on Tuesday. “The outcry was phenomenal, not only from people demanding that something be done, but also from several potential plaintiffs.”

The ACLU investigation could lead to a potential lawsuit that would unite complainants as plaintiffs against the state.

The three-part NPR report described Native American children as being placed in South Dakota's foster care system at a disproportionate rate: More than half of all children in foster care are Native American, despite them accounting for just 15 percent of the state's child population.

The series suggested that the motive might be money, since the state gets federal financial assistance for each child removed from his or her home. It also suggested a conflict of interest in Gov. Dennis Daugaard's work for Children's Home Society of South Dakota when he was a lieutenant governor. That organization received millions of dollars for housing Native American children under contracts the state awarded without competitive bid.

The governor's office criticized the report and went on the defensive even before the series began airing last week, releasing a memo titled “Setting the Record Straight” that accused NPR's reporter of being unfair and biased. According to the memo, Children's Home Society has had contracts with the state since 1978, long before Daugaard became its chief operating officer in 2002.

While Walker commended the NPR report, she said the ACLU isn't out to attack the governor.

“It's not about the governor. It's about these kids,” she said. “They deserve someone to check into this.”

At the center of the conflict, she said, is a merging of state, federal and tribal jurisdiction that is difficult to navigate. The ACLU hopes the spotlight on the issue will prompt new legislation to make it easier for child-protective services workers to do their jobs.

On its website, NPR describes the three-part series as the culmination of a yearlong investigation.

“Some children are removed from their homes for legitimate reasons,” the series' introduction reads. “But in South Dakota very few are taken because they've been physically or sexually abused. Most are taken under a far more subjective set of circumstances.”

After the series began airing, two members of Congress – U.S. Reps. Ed Markey, D-Mass, and Dan Boren, D-Okla. – sent a letter to the Interior Department of Indian Affairs calling for an investigation.

“If the information on the NPR article is accurate, it would appear that the state of South Dakota has failed not only to abide by the mandates of federal law but also failed its Indian children, their families and their tribes by violating the letter and spirit” of the Indian Child Welfare Act, the congressmen wrote to Larry Echo Hawk, Indian Affairs' assistant secretary.

The federal law was passed in 1978 to help ensure that Native American children weren't separated from their families and tribes through involuntary removal.

Gubernatorial aide Tony Venhuizen told the Rapid City Journal it was unfortunate that two members of Congress representing other states didn't contact South Dakota officials before seeking an investigation into allegations about the state.

“These congressmen based their letter on an NPR report that was deeply flawed,” he said. “It's really too bad that they took this step without even asking the Department of Social Services or anyone in South Dakota for the facts.”

Walker, the ACLU spokeswoman, said the NPR piece highlighted an important and overlooked issue affecting Native American families.

“I have much respect for the (Department of Social Services) workers. I have to imagine that meeting all of the requirements they have to meet can get tricky,” she said. “I think that some statutory legislative could potentially ease some of the burden.”