AUSTIN, Texas (AP) — Land Commissioner George P. Bush and his agency are joining families suing the federal government, accusing it of unconstitutional seizure of land along the Texas-Oklahoma border.

In a motion filed Tuesday in U.S. District Court, the General Land Office joined a lawsuit brought last month by seven landowning families. Three Texas counties and a county sheriff's office have also joined the suit.

It accuses the federal Bureau of Land Management of a "blatant land grab" involving a 116-mile tract along the Red River. The river marks the border between Texas and Oklahoma but its waters have shifted for decades, raising ownership questions.

Bush's office controls Texas' public lands and says 113 acres of its holdings may be affected. Federal officials say they want to work with area residents to determine proper ownership.

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