A rift is widening between Native American groups in New England over who has claim to scores of acres south of Boston where one tribe has been trying for years to build a $1 billion casino.

The recently revived Mattakeeset Massachuset Tribe argues it’s the rightful heir to the land in Taunton set aside by the federal government for the Mashpee Wampanoag Tribe, which is planning to build a hotel, casino and entertainment complex.

The Mattakeesets want the Mashpees and state and local authorities to recognize their land claim, which they base on colonial-era documents.

“They blatantly fooled the whole entire country about this land belonging to them,” said Larry Fisher, who has been working to revive the tribe since becoming its chief sachem in 2014, of the Mashpees. “We just want the truth to be told. It belongs to us. The Mattakeesets.”

The Mashpee Wampanoag Tribe, which famously traces its ancestry to the Native Americans who shared a fall harvest with the Pilgrims 400 years ago, counter that Fisher’s group is just a smaller band within the broader Wampanoag people who have inhabited Massachusetts for thousands of years.

The Mattakeeset Tribe currently has a few hundred members, according to Fisher, but does not have federal recognition or a land base like the Mashpee Tribe, which was federally recognized in 2007 and has roughly 3,000 members.

“Larry is well-meaning but very confused,” said Steven Peters, the Mashpee Tribe’s spokesman. “The Mattakeesets and the Massachusets are Wampanoags.”

The dustup is the latest wrinkle in the Mashpee Wampanoag Tribe’s tortured, years-long quest for federally protected land – and the lucrative rights to build a tax-exempt casino on it.

The Cape Cod-based tribe was granted a more than 300-acre reservation in the waning months of the Obama administration in 2016, but the Trump administration moved to revoke the reservation in what the tribe and its supporters complained was a dangerous precedent. A federal judge in June halted the move; the Interior Department has appealed.

Meanwhile, the tribe’s prominent, longtime chairman was arrested last month on federal bribery charges in connection with the casino project. Cedric Cromwell has denied the allegations, but has been ousted as chairman by tribe leaders.

Fisher said his tribe has no quarrel with the half of the tribe’s roughly 300-acre reservation that’s located in the town of Mashpee on Cape Cod, where the tribe has operated a government center and other tribe services for years.

But he contends the Taunton-area half, located some 50 miles (80 kilometers) from Mashpee, was never part of the rival tribe’s historic territory.

Fisher points to a book published last month by Jeremy Bangs, founder of the Leiden American Pilgrim Museum in the Netherlands, which argues that a 1664 deed designated the lands as the “Titicut Reserve” and specifically set it aside for the Mattakeesets in perpetuity. Fisher says the deeded lands encompass all of what is today Taunton, Middleborough and Bridgewater, as well as parts of Duxbury.

Complaints that the Mashpees are inflating their ancestral territory at the expense of other Native Americans aren’t new. At least two members of other Massachusetts tribes have raised the issue in recent years, and local casino opponents have made similar arguments in their long-running federal court challenge.

The state Commission on Indian Affairs hasn’t officially waded into the debate, but John Peters, the agency’s executive director and a member of the Mashpee Wampanoag Tribe, was skeptical of the rival tribe’s claim.

“To give credibility to a self-proclaimed chief of a tribe that hasn’t been heard of in several hundred years demeans the integrity of our culture,” he said.