Rochester Public Schools were closed Monday after the district detected what it calls “unusual activity” in its technology network.

According to a news release, the school district’s technology staff detected the issue on Thursday and shut down its network and most of its “core technology systems” in response.

Families and staff first learned about the incident on Friday.

The school district says it’s now working to investigate the issue and give faculty time to prepare lessons without or with reduced technology. RPS asked students not to come to school on Monday so staff can prepare for Tuesday.

“We regret the impact that not having students report on Monday will have on our families and we also regret needing to share this information during what for many of our families is a holiday weekend and at the end of spring break,” the school district said in a statement. “We ask for your patience and understanding as we work to resolve this situation as quickly as possible.”

Sports and other extra-curricular activities are not expected to be impacted, and the district’s child care program will still be operational Monday from 8:30 a.m. to 4:30 p.m. at the Northrop Community Education Center.

RPS officials did not immediately disclose the nature of the activity on its network but said they will provide further updates as they learn more.

The incident in Rochester comes after a ransomware attack hit Minneapolis Public Schools earlier this year. Hackers accessed years of personal data from students, families and staff members and eventually posted the information online.

Twin Cities cybersecurity expert Rick Engelhardt says schools can be an easy target without the cybersecurity of financial or medical institutions.

“It is a pretty open target because generally, you’ve got one or two IT guys, maybe they’re taking care a few different schools,” Engelhardt said.

Personal data obtained by hackers in a cyberattack against a school can be used against students years later.

“The thing that I think is interesting with the schools is this is a target set that is going to kind of grow over the coming years,” Engelhardt said. “Right now, you’re seeing the targets being the identities and profiles of a young student. There’s going to be a lot of correlation with that data and it’s going to get more and more valuable because it’s just something we just can’t get away from anymore.”