Pennsylvania Attorney General Josh Shapiro said he's investigating opioid manufacturers, along with attorneys general in at least 25 other states.

The announcement comes after other states and counties have filed lawsuits alleging pharmaceutical companies helped create the crisis.

AG Shapiro didn't give many specifics on the investigation, only saying that it involved a group of Republican and Democratic attorneys general from across the U.S.

His office said it includes subpoenas for documents and testimony from the manufacturers of opioids.

But he wouldn't say how many states were participating, what companies are being targeted, or whether it was civil or criminal in nature.

"I want you to know that I will follow the evidence to hold everyone, everyone accountable and responsible no matter how big or powerful they are," said Shapiro.

Others have filed lawsuits recently, including Mississippi, Ohio, and counties in Illinois, New York and California.

Some legal experts have said these cases will be more difficult than the landmark 1998 tobacco settlement, because the opioid pills aren't being used as directed. The most aggressive drug company - Purdue - also made changes after a settlement with the federal government in 2007.

"This is a broad, bipartisan, multi-state investigation of which Pennsylvania is one of the lead states. We have made great progress in it, and we're going to continue to work diligently in this effort," Shapiro adds.

Drug overdoses killed more than 4,600 people in Pennsylvania last year.