The Manhattan district attorney’s office said on Saturday that it is investigating a sexual assault allegation against Eric Swalwell, a Democratic congressman from California running to be the state’s governor, who on Friday denied claims by an unnamed woman that he sexually assaulted her twice.

Confirmation of an investigation came after the San Francisco Chronicle reported on Friday that a woman who previously worked in Swalwell’s district office accused him of two nonconsensual sexual encounters.

She was quoted in the newspaper’s report as saying she had been too intoxicated on both occasions – in California in 2019, when she worked for Swalwell, and then in New York in 2024 – to consent to sex.

New York law holds that a person cannot consent to sexual activity if they are “mentally incapacitated” or “physically helpless” due to drugs or alcohol, but in some cases voluntary intoxication may not legally negate consent.

In an on-camera interview with CNN in which her face was obscured, the woman directly accused Swalwell of raping her in New York. The broadcaster also reported that three other women accused Swalwell of sending them inappropriate sexual messages, including naked images, and unwanted touching.

The Manhattan district attorney’s office urged anyone with knowledge of the allegations to contact its special victims division.

“Our specially trained prosecutors, investigators, and counselors are well-equipped to help you in a trauma-informed, survivor-centered manner,” the DA’s office said in a statement to CNN.

Swalwell has denied the accusations as “absolutely false” and suggested they were politically motivated. He noted that they come ahead of the June primary in the governor’s race replace Gavin Newsom, the outgoing governor, in which Swalwell was one of the leading contenders to advance to a top-two runoff after a non-partisan primary in June.

“These allegations of sexual assault are flat false. They’re absolutely false. They did not happen, they have never happened, and I will fight them with everything that I have,” the congressman said on Friday.

The allegations, which have not been independently verified by the Guardian, were published four days after Swalwell told reporters in Sacramento he’d never had a sexual relationship with a staff member or intern.

Swalwell said in a video statement on social media that he would spend the weekend with family and friends and share an update “very soon”.

Staff at Swalwell’s office condemned the alleged behavior by the Democratic congressman.

“We stand with our former colleague, and the other women who have come forward. We believe you should stand with them, too,” the statement, obtained by the Washington Post, said. “The behavior detailed in these reports is abhorrent, beneath the dignity of those serving in public office and betrays the trust of all Californians.”

They said that “any decision of staff members to remain in their roles in the interim should not be viewed as support” for Swalwell.

The Manhattan DA’s investigation came a day after prominent supporters of Swalwell’s bid for governor began to withdraw their backing, including all 21 of his backers in Congress.

A number of leading California Democrats, including both of the state’s senators and its lieutenant governor, urged Swalwell to end his campaign.

Former House speaker Nancy Pelosi, who hasn’t endorsed any candidate in the race, said the “serious allegations” must be investigated. She said she spoke to Swalwell and suggested that be done “outside of a gubernatorial campaign”.