Minneapolis Public Schools sent an email to families Friday saying the district has begun contacting people who may have had their personal information accessed in the February cyberattack on the district.

"Notification letters should arrive at homes within the next two weeks," the email read.

The district became aware of what it first called an "encryption event" on Feb. 18 when computer systems were down. An investigation showed that a hacker had accessed information in the systems between Feb. 6 and Feb. 18.

In March, a ransomware group claimed responsibility for the attack on Minneapolis Public Schools and posted a $1 million ransom, along with a 51-minute video — since removed — with screenshots showing a wide variety of information. The data it displayed included student names and addresses and forms that could contain sensitive employee information.

"Understanding what information had been impacted was critical," the Friday email to families said. The district partnered with national specialists to do a "comprehensive review" of the computer systems involved to determine what sensitive information was accessed and identify those who were impacted.

"This process was time-intensive and required both computer-assisted and manual review," the email read. "Although it has been difficult to not share more information with you sooner, the accuracy and the integrity of the review were essential."

The district is offering free credit monitoring to people who were affected by the data breach and has connected others to a service to address "mental or emotional responses to this incident," according to the email.

District policies and procedures are undergoing review, protections have been added and staff is receiving additional training to help prevent other cyber security issues, the statement said.

The email thanked families for their patience and referenced how the frequency of such incidents is increasing for organizations like school districts. That trend has prompted a dramatic rise in cyber liability insurance premiums.

The school district's announcement came days after the University of Minnesota acknowledged that it's trying to determine how many people might have been affected by a potentially massive data breach there — and precisely who they are, so it can send notices as well.

A July 21 report from the Cyber Express, a cybersecurity news site, outlined a hacker's claims to have accessed some 7 million Social Security numbers dating to 1989. The report said the hacker accessed the university's data warehouse to analyze the effects of affirmative action following the U.S. Supreme Court ruling that limits the consideration of race and admissions decision. The FBI and the Minnesota Bureau of Criminal Apprehension are investigating.

Staff writer Liz Navratil contributed to this report.