HOUSTON (Reuters) - SandRidge Energy Inc (>> SandRidge Energy Inc.) is the target of federal grand jury probe concerning violations of antitrust law related to the leasing of oil and gas properties, the company said in a regulatory filing on Thursday.

The Oklahoma City, Oklahoma company said the transactions subject to the government's inquiry date from 2012 and prior years, according to the filing with the U.S. Securities and Exchange Commission.

"We are taking the matter very seriously and continue to work with the DOJ in the course of the investigation, however we will not comment beyond our disclosures," said Jeff Wilson, vice president of government and public affairs at SandRidge.

SandRidge was told April 7 by the U.S. Department of Justice it is a target of an Oklahoma grand jury, the filing said.

SandRidge's former chief executive officer Tom Ward was ousted by the company's board in January 2013 after the company’s biggest investors alleged governance lapses and strategic missteps.

Aubrey McClendon, who co-founded Chesapeake Energy with Ward in 1989, is also under investigation by the DOJ for potential violations related to leasing oil and gas properties, according to a regulatory filing last month from a McClendon-affiliated firm.

McClendon, now CEO of American Energy Partners, did not immediately respond to emailed questions seeking comment on whether he is subject to any grand jury investigation. Ward did not respond to a message requesting comment left at his Oklahoma-based oil and gas firm.

Chesapeake also previously disclosed it is cooperating with a government probe into possible antitrust violations.

It is not clear if the investigations are related and a spokesperson for the U.S. Department of Justice declined to comment. A representative for Chesapeake did not immediately respond to a call for comment.

The DOJ said in 2012 it was investigating potential antitrust violations related to oil and gas land leasing. Among the companies subject to the probe were Chesapeake and Canada’s Encana Corp. (>> Encana Corporation).

The two had been involved in land leasing in Michigan in 2010 and Reuters reported they had communicated with each other on ways to suppress land lease prices in the state during a leasing boom (reut.rs/1ieHE8D).

Both companies denied wrongdoing and were told last year the DOJ had ended its probe into their leasing activities in Michigan.

Although the DOJ closed its investigation in Michigan, its antitrust division said last year the investigation was continuing in other regions, without citing which companies remained subject to the probe.

(Reporting by Anna Driver; Editing by Terry Wade and Diane Craft)

By Anna Driver and Joshua Schneyer