The FBI is investigating an apparent breach of its jobs website as a criminal hacking group claimed to have accessed “very sensitive data” on nearly all agents and job applicants.

“The FBI is aware of claims regarding unauthorized activity affecting FBIjobs.gov and is currently investigating,” the bureau said in a statement. The website, the main portal for prospective employees to learn about the FBI and initiate the application process, remained offline Wednesday morning.

A message that circulated online from a hacking group known as ShinyHunters claimed responsibility for the hack.

The message, directed to FBI director Kash Patel as well as the assistant director in the charge of the FBI’s cyber division, said the hacking group had “compromised very sensitive data on almost ALL FBI Agents and individuals who filed an application with the FBI for a job”.

The claims could not immediately be verified, and an FBI spokesperson declined to comment further. An email to an address associated with the organization was not immediately returned.

In its message, ShinyHunters said it would give the bureau one week to correct or remove what it says are false allegations in an FBI public service announcement from May that described the organization as a “cyber criminal group specializing in large-scale data breaches and extortion”.

That announcement characterized ShinyHunters as “threat actors” who often “use their real or exaggerated claims of access to sensitive or personal information to prompt payment from victims”, commonly harass or threaten victims and “may falsely claim to have sensitive or compromising information, including embarrassing photographs or videos of victims, which frequently do not exist.”

ShinyHunters said in its message to the FBI that it was “offended” by those characterizations and demanded that the FBI remove those claims.

The FBI has been a common hacking target.

In March, the FBI disclosed that it was investigating “suspicious activities” on an internal system that contains sensitive information related to surveillance operations and investigations. Also that month, a pro-Iranian hacking group claimed to have hacked an account of Patel’s and posted online what appear to be years-old photographs of him, along with a work resume and other personal documents dating back more than a decade.