The computers of the House Democratic campaign committee have been hacked, an intrusion investigators say resembles the recent hacking of the Democratic National Committee (DNC) for which the Russian government is the leading suspect.

The digital break-in at the Democratic Congressional Campaign Committee (DCCC), which the organization acknowledged on Friday, added another layer of mystery to the hacking of Democratic party information that has been revealed in the heat of this year’s presidential and congressional elections.

Details were initially unclear about who hacked the computers and which information was accessed at the DCCC, which raises money and provides other assistance for Democratic House candidates. Spokeswoman Meredith Kelly said the committee was “the target of a cybersecurity incident” and had been informed by investigators “that this is similar to other recent incidents, including the DNC breach”.

Barack Obama has said Russia was almost certainly responsible for the hack of the DNC, an assertion with which cybersecurity experts have agreed. That breach led to the release by WikiLeaks on 22 July, days before the Democratic national convention began, of 19,000 emails showing that supposedly neutral party officials were favoring Hillary Clinton over Senator Bernie Sanders during their primary contest for the presidential nomination.

As a result of that disclosure, the party chairwoman, Debbie Wasserman Schultz, announced her resignation this week.

Kelly said the DCCC was using CrowdStrike, a computer security firm based in Irvine, California, and was “cooperating with the federal law enforcement with respect to their ongoing investigation”. She said her organization was “continuing to take steps to enhance the security of our network in the face of these recent events”.

A House Democratic aide said late on Thursday that the FBI was investigating the hack. The aide was not authorized to discuss an ongoing investigation and spoke on condition of anonymity.

The White House deputy press secretary, Eric Schultz, said he was aware of the reports about hacking but referred questions to the FBI. The FBI did not immediately respond to a request for comment.

CrowdStrike issued a statement confirming its work for the congressional campaign committee but provided no additional details.

Computer hacking, emails and indications of Russian involvement have evolved into a political issue in the presidential campaign between Clinton and the Republican candidate, Donald Trump.

This week, Trump encouraged Russia to seek and release more than 30,000 other missing emails deleted by Clinton, the former secretary of state. Democrats accused him of trying to get a foreign adversary to conduct espionage that could affect this November’s elections, but Trump later said he was merely being sarcastic.

Clinton deleted the emails from her private server, saying they were private, before handing other messages to the state department. The US justice department declined to prosecute Clinton over her email practices, though the FBI director, James Comey, called her “extremely careless” in handling classified information.

CrowdStrike and another security firm, ThreatConnect of Arlington, Virginia, said they found evidence pointing to Russian government involvement in the DNC hack when they analyzed the hackers’ methods and efforts to distribute the stolen emails and other files. The hacker groups, identified by CrowdStrike as Cozy Bear and Fancy Bear, used different but sophisticated techniques to break into the DNC and try to avoid detection.

The DCCC hack was first reported by Reuters.