The Department of Homeland Security and the Justice Department are investigating a claim that personal data related to thousands of DHS and FBI employees was hacked and has been posted online, an agency spokesman said Monday.

The tech website Motherboard reported on Sunday that a hacker, who Motherboard said wished to remain anonymous, intended to dump onto the Internet names, job titles, email addresses and official phone numbers of more than 9,000 DHS employees and an additional 20,000 FBI workers.

The SITE Intelligence Group, which monitors militant media activity, on Monday said a pro-Palestinian Twitter account on Sunday had posted a link to a document that contained the purported data of 9,372 DHS employees.

The posted data included DHS employees’ names, job titles, departments, phone and fax numbers, state and country address information, and official dhs.gov email addresses, SITE said.

SITE said the hack bore a strong resemblance to earlier breaches attributed to a group called “Crackas with Attitude” that had been implicated in attacks targeting CIA Director John Brennan, FBI Deputy Director Mark Giuliano and Miami police.

However, a government official familiar with investigations into the breach said some data published by the hacker relates to people who stopped working for DHS more than a year ago.

S.Y. Lee, a DHS spokesman, said, “We are looking into the reports of purported disclosure of DHS employee contact information. We take these reports very seriously, however, there is no indication at this time that there is any breach of sensitive or personally identifiable information.”

Peter Carr, a spokesman for the Justice Department, said, “The department is looking into the unauthorized access of a system operated by one of its components containing employee contact information.”

“This unauthorized access is still under investigation; however, there is no indication at this time that there is any breach of sensitive personally identifiable information,” Carr said.

Britain’s Daily Telegraph reported that one of the hackers who claimed to be behind the latest breaches is a British man and former member of a hacker group called Lizard Squad that claimed responsibility for hacking popular gaming systems in late 2014.