Updated

Several top aides to Texas Gov. Rick Perry appeared Friday before a grand jury investigating whether the governor abused the powers of his office with a 2013 veto.

Mike Morrissey, Perry's deputy chief of staff; Ken Armbrister, legislative director; Rich Parsons, a Perry spokesman; and Mary Anne Wiley, the governor's general counsel, declined comment on their way in and out of the grand jury room.

Friday was the first time Perry's staff has been seen entering the grand jury room at the Travis County courthouse in relation to the investigation.

The panel is looking into whether Perry broke the law when he vowed to veto funding for the office of Travis County District Attorney Rosemary Lehmberg's anti-corruption unit if the Democrat didn't resign after a drunken driving arrest.

Lehmberg refused to resign and Perry vetoed $7.5 million. A political watchdog group then filed a complaint alleging that Perry tried to coerce Lehmberg to leave office.

The probe could be a problem for Perry, who is considering making another run at the White House in 2016. The longest serving governor in state history, Perry is not seeking another state term, which ends in January 2015.

Perry has said he never sought a deal with Lehmberg and his aides insist the governor was within his rights to exercise his line-item veto power the way he that did.

Grand jury proceedings are secret and none of Perry's staff who went in the room would say if they were subpoenaed or came voluntarily. It was unclear if Wiley was a witness or providing legal counsel. She escorted each of the others out of the building at different times over the afternoon.

Michael McCrum, the special prosecutor investigating Perry, has said he has specific concerns about Perry as part of the investigation, though he has refused to elaborate. No charges have been filed.

"It's proceeding methodically and we're doing our best to understand what happened," McCrum said. He said the panel would reconvene June 6 and would likely meet again after that, but declined further comment.

Perry spokeswoman Lucy Nashed refused to say if Perry has been subpoenaed.

"We respect the longstanding legal principle of grand jury confidentiality and therefore it would be inappropriate to comment on the proceedings.

The veto in question was made in accordance with the veto power afforded to every governor under the Texas Constitution, and we remain ready and willing to assist with this inquiry," Nashed said.

Lehmberg said earlier this week that Perry's personal attorney made an unusual request to the judge who seated the grand jury to be allowed to use a discreet entrance away from reporters staking out the main doorway. There is a private entrance to the grand jury room through Lehmberg's office, but the Perry staff members used the main door Friday.