HARRISBURG -- A sweeping grand jury investigation into allegations of government corruption has extended further into the House Republican caucus.

Some caucus staffers have been subpoenaed to provide grand-jury testimony, House Republican spokesman Steve Miskin confirmed yesterday. He did not know which staffers or how many. He said he was not aware of any subpoenas issued to lawmakers.

Some caucus staffers already have appeared voluntarily before the grand jury, he said.

So far, the investigation's focus appears to have been on House Democrats, including 12 who were arrested last month for misusing tax dollars to finance political campaigns. Democrats, including those arrested, have complained that Attorney General Tom Corbett, a Republican up for re-election, has ignored GOP caucuses.

Mr. Corbett has repeatedly assured that he is investigating all four caucuses to determine whether public funds were misappropriated.

The investigation has involved hundreds of witnesses and thousands of pages of government records.

The investigation was spurred by newspaper reports of secret bonuses given to House Democratic staffers who had worked extensively on incumbents' campaigns in 2006.