*Editor's note: This story has been updated throughout. 

A Collin County grand jury is investigating whether a land sale tied to a business group involving Texas Attorney General Ken Paxton was improper.

Miles Brissette and former state District Judge Bob Gill were appointed special prosecutors on Nov. 13 by state District Judge George Gallagher of Fort Worth to investigate criminal allegations into a land sale involving a limited partnership, called Eldorado-Collin, that included Paxton, Collin County District Attorney Greg Willis and eight other partners. The investigation is separate from the securities fraud charges that Paxton is facing.

The two attorneys released a joint statement Friday afternoon in which they confirmed they were appointed to "investigate a matter as special prosecutors" and declined further comment. 

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"While they may be referred to as special prosecutors, at this juncture they are merely investigating whether anyone engaged in improper conduct in connection with the sale of the property," said Bill Mateja, a member of Paxton's legal team in the securities fraud case. 

"We have cooperated fully with the Fort Worth attorneys and are confident that they will find no wrongdoing on the part of General Paxton or anyone involved," Mateja said. 

The Eldorado-Collin LP partnership bought 35 acres of undeveloped land in McKinney for about $700,000, The Dallas Morning News reported in 2014. The partnership later sold part of the land to a real estate development company called Cornerstone for $1 million. That land would later become the site of the Collin Central Appraisal District.

The Morning News reported that before Cornerstone bought the property, Eldorado-Collin officials sought and received a critical zoning change from McKinney that cleared the way for an appraisal district building to be built on the land. Paxton told the Morning News he had no role in the rezoning efforts. It is not clear what aspect of the land deal is being investigated.

"Importantly, the property was sold not by General Paxton nor any business he was involved in but by a real estate company named Cornerstone with which Paxton had no involvement," Mateja said. "Cornerstone had earlier purchased the property from a limited partnership in which Paxton was merely a limited partner. Paxton was not involved in the sale to Cornerstone, which is typical of a role of a limited partner."

Brian Wice, a special prosecutor in the pending criminal case against Paxton, declined to comment on the new investigation. 

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Paxton was indicted last year on charges he misled investors in a technology company before he was attorney general. He has pleaded not guilty to three felony charges.