Hackers attacked the Fairfax County Public Schools computer system and placed ransomware on some of its systems, a school district spokesperson said Friday.

The district, which serves 189,000 students in northern Virginia, said it had recently learned of the attack and it is working with its security experts to investigate the scope of the attack and determine what information was stolen. Ransomware is software used to steal and then threaten publication of data or block access unless a ransom is paid.

“We are taking this matter very seriously and are working diligently to address the issue,” FCPS spokeswoman Lucy Caldwell said in a statement. “We have retained leading security experts to help us investigate the matter and recover from the situation. We also are coordinating our efforts with law enforcement authorities. The protection of our students’ information is a top priority for Fairfax County Public Schools.”

According to InfoSecurity magazine, the hacker group MAZE posted on its website that it had successfully infiltrated the school district’s site with ransomware. The group offered proof of its attack by uploading a zip file of data it stole from the school system, the magazine said.

The district said it was working with its security experts and the FBI to determine the impact on its data. It said it will notify affected parties based on the results of the investigation.

“We currently believe we may have been victimized by cyber criminals who have been connected to dozens of ransomware attacks in other school systems and corporations worldwide,” the district wrote in an email to everyone in the school system Friday evening. “We will work with law enforcement to the fullest extent to prosecute any individuals or groups that attack our systems.”

District officials did not immediately respond to questions about whether the security breach interrupted online learning Friday or whether it would affect the resumption of online learning next week. The district also did not immediately respond to questions about the nature of the demand made by the hacking group.

Tina Williams, president of the Fairfax County Federation of Teachers, said in a statement that the union was “shocked to learn that the FCPS system has been hacked.”

“This is deeply alarming for our community and we urge FCPS to swiftly resolve the issue, take every action possible to maintain the safety of employee and student data and information and keep the FCPS community informed of all developments,” she said.

This is the second major computer problem for the school district this year. In April, the school district’s technology chief stepped down following a badly flawed rollout of its online learning. The attempt to introduce distance learning in response to the coronavirus pandemic was beset by massive technological glitches, privacy breaches and online harassment. The district was forced to halt classes for several days to address all of the issues.