HARRISBURG — The Dauphin County District Attorney’s Office has opened a criminal investigation into allegations that a Western Pennsylvania lawmaker had sex with a woman while she was incapacitated and without her consent, according to multiple sources with knowledge of the inquiry.

State Rep. Brian Ellis, a Republican from Butler County, is alleged to have taken the woman to his Harrisburg residence, where the alleged assault occurred in late 2015, the sources said. Details about what triggered her incapacitation were not available.

The woman, a state employee who does not work for Ellis, has alleged that the lawmaker told her the next morning that the two had had sex. Prior to that evening, she has said, Ellis had pursued her and she had made it clear she did not want to be involved with him.

Ellis, 49, has not publicly responded to the allegations. He did not return multiple calls from reporters this month to his legislative offices and cell phone. He did not answer emails seeking an interview or a letter detailing the allegations against him that was delivered to his offices in the state Capitol and his district, as well as his homes in Harrisburg and Butler Township, which is near Pittsburgh. It is not known whether he has a lawyer.

Reached for comment, District Attorney Fran Chardo would say only, “I don’t comment on criminal investigations, unless they are already publicly known."

Jennifer Storm, the state’s victim advocate, said she was working with the victim. She declined to confirm the existence of any investigation.

But Storm, whose office provides victims of crime with support and advocacy services, said the woman had given “thoughtful consideration to all her options” for months before making the decision to talk about what happened to her.

“It’s an incredibly bold and courageous act to come forward when your perpetrator is powerful,” said Storm, later adding: “This is a very hard time for her.”

State Rep. Brian Ellis
Pennsylvania House of Representatives
State Rep. Brian Ellis

Top lawyers for House Republicans learned of the allegations against Ellis early last year, and told the person who reported them to contact Chardo’s office because they appeared criminal in nature, according to a legislative source with knowledge of the matter. They also provided information about the House Republican caucus' sexual harassment policy and the procedure for filing a complaint with them.

Late Thursday afternoon, House Republicans issued a statement that did not name Ellis but restated their “zero tolerance” for sexual violence or harassment and a pledge to assist in any investigation related to it.

“Our caucus has not been contacted by any law enforcement agencies regarding any new or ongoing investigations," it said. “If criminal charges related to sexual violence or harassment are filed against one of our members, we would expect an immediate resignation.”

The Inquirer and Daily News and the Caucus are withholding the woman’s name because the newspapers do not identify victims of alleged sexual assault unless they agree to be named.

The alleged assault occurred in late October 2015, according to multiple interviews with people familiar with the allegations. The woman could not consent because she was severely impaired, they said.

In an interview, the woman has said she had struggled emotionally with coming forward.

Ellis, an advocate for business and gun-owner rights first elected to the House in 2004, is the second Republican House member in less than a year to be investigated by Chardo’s office on assault allegations.

Last year, two women filed a complaint with House Republicans, alleging they were physically or sexually abused by then-State Rep. Nick Miccarelli (R., Delaware).

House Republican lawyers investigated the claims and found the women credible. They called on Miccarelli to resign, but he denied the claims and served out his term, which ended last year.

Last month, Chardo ended his investigation into those claims and announced that no charges would be filed against Miccarelli, in part because one of the accusers chose not to go forward. She said her decision was based on the emotional trauma of the process and “the prospect of a long and drawn-out criminal proceeding."

Mike Wereschagin of the Caucus contributed to this article.