The Railroad Commission of Texas is ordering subsidiaries of ExxonMobil Corp. (NYSE: XOM) and Houston-based EnerVest Ltd. to prove their wells aren't responsible for North Texas earthquakes.

The commission said April 24 it has initiated proceedings requiring the operators of disposal wells near Azle, Texas, to prove the injection permits for the wells should not be cancelled and the wells shut-in. The order follows a study on recent seismic activity in North Texas published last week by Southern Methodist University (SMU) researchers.

The disposal wells involved are XTO Energy Inc.’s West Lake SWD No. 1, in the Newark, East (Barnett Shale) Field in Parker County, and EnerVest Operating LLC’s Briar No. 1 in the Caughlin (Strawn) Field in Wise County.

The hearings for XTO, based in Fort Worth, Texas, and EnerVest are slotted for June. The SMU report remains under review by commission staff.

“The Railroad Commission has in place strong rules addressing the issue of seismicity and disposal well activity, and it is incumbent upon us to apply these rules where and when appropriate for the protection of public safety and our natural environment,” said Chairman Christi Craddick in a statement. “In light of SMU’s study linking disposal well activity to earthquakes in 2013, it is important to assess this new information in relation to the continued operational safety of the wells.”

Commissioner David Porter said in a statement, “Due to the that fact the wells were permitted prior to the commission’s rule amendments addressing disposal well activity and seismic activity, and in light of the new research contained in SMU’s report, it’s appropriate and necessary for the commission to consider the operation of these wells in a fully informed manner and determine the appropriate course of action.”