The Oklahoma Attorney General’s Office is looking into a complaint involving a group of donors to Tulsa County Sheriff Vic Regalado’s special election campaign, according to several sources familiar with the matter.

The sources told the Tulsa World on the condition of anonymity that the AG’s Office is handling an ethics complaint filed in March by the Tulsa County Democratic Party. The complaint alleges donors tied to ISTI Plant Services in Rogers County may be straw donors.

It’s unclear if the case has or will come before the state multicounty grand jury, which is under the direction of the Attorney General’s Office. The panel will convene Tuesday through Thursday and again July 12-14.

Will Gattenby, AG’s Office spokesman, said the agency typically doesn’t comment on whether an investigation has been launched or the progress of ongoing probes.

Regalado told the World he hasn’t been contacted by any investigators or the multicounty grand jury.

“We have gone above and beyond the law to ensure each of our donations were legal and appropriate, and will continue to do so,” Aaron Brewer, campaign manager for Regalado, said in a statement.