July 8, 2013: Texas Attorney General Greg Abbott speaks during an anti-abortion rally at the State Capitol in Austin, Texas.REUTERS

Texas officials are raising alarm that the Bureau of Land Management, on the heels of its dust-up with Nevada rancher Cliven Bundy, might be eyeing a massive land grab in northern Texas.

The under-the-radar issue has caught the attention of Texas Attorney General Greg Abbott, who fired off a letter on Tuesday to BLM Director Neil Kornze saying the agency “appears to be threatening” the private property rights of “hard-working Texans.”

“Decisions of this magnitude must not be made inside a bureaucratic black box,” wrote Abbott, also a Republican gubernatorial candidate.

CLICK HERE TO READ ABBOTT'S LETTER

At issue are thousands of acres of land on the Texas side of the Red River, along the border between Texas and Oklahoma. Officials recently have raised concern that the BLM might be looking at claiming 90,000 acres of land as part of the public domain.

The agency, though, argues that any land in question was long ago determined to be public property.

“The BLM is categorically not expanding Federal holdings along the Red River,” a BLM spokeswoman said in a written statement late Tuesday afternoon.

The spokeswoman referred to a 140-acre plot “determined to be public land in 1986” – an apparent reference to a 1986 federal court case. Breitbart.com,which reported Monday on the Texas land dispute, reported that a Texas landowner lost 140 acres to BLM in that case, and the agency is now using that decision as precedent to pursue more property.

According to background materials put out by Texas Republican Rep. Mac Thornberry’s office, the BLM is revisiting its management plan for lands including those along a 116-mile stretch of the Red River. His office said the possibility has been discussed of opening that land up for “hunting, recreation and management.”

Abbott, in his letter to the agency, said “it is not at all clear what legal basis supports the BLM’s claim of federal ownership over private property.” He said private landowners have cultivated the property “for generations.” 

The debate comes on the heels of a tense standoff earlier this month in Nevada, after BLM tried to round up cattle owned by rancher Cliven Bundy – the product of a long-running dispute over unpaid grazing fees. Hundreds of states’ rights supporters, some of them armed, showed up to protest, and BLM back off citing safety concerns.

In the Texas matter, the Supreme Court incorporated the Red River as part of the border with Oklahoma nearly a century ago.

Congress further clarified the boundaries of the two states in 2000. 

It’s unclear how seriously BLM might be looking at laying claim to additional boundary land.

BLM said it is merely in the “initial stages of developing options for management of public lands,” as part of a “transparent process with several opportunities for public input.” 

BLM Field Manager Stephen Tryon, in a March 17 letter to Thornberry, said officials would eventually look to “ascertain the boundary” between federal and private land and acknowledged residents’ concerns that new surveys could “create cloud to their private property title.”

But he said no new surveys are currently planned, and reiterated that there are no federal claims to Texas land “as defined by multiple rulings of the U.S. Supreme Court.”

FoxNews.com’s Judson Berger contributed to this report.