An apparent cyberattack on Iowa's largest school district has led officials to cancel classes for 30,000 students for a second day as technicians scramble to protect data and restore the computer system, the district's leader said Tuesday afternoon.

The Des Moines school district's interim superintendent, Matt Smith, said officials received an alert Monday about a possible "cybersecurity event" that led them to cancel classes Tuesday and then to keep schools closed Wednesday. On Tuesday night, the district announced that school would reopen Thursday.

"When our system is down, it impacts every aspect of our organization," Smith said, noting everything from school bus routes to lunch menus are controlled through the computer system.

DES MOINES, IA, SCHOOLS CLOSED FOLLOWING APPARENT CYBER ATTACK

Smith said it wasn't clear what had happened to the computer system.

"It was a cybersecurity event that we can't confirm yet until we run through all of our diagnostics and all of our protocols to get the forensics back to understand that specifically," Smith said. "What I can tell you is we are operating as if it is a ransomware attack just to be sure."

Smith said federal and state authorities were helping the district respond to the problem.

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Although there are plenty questions about what happened, Smith said officials believe the payroll system is safe and that its nearly 5,000 teachers and staff can be paid. The district also has restored its website, which enables it to communicate updates more easily.

Apparent ransomware attacks have targeted many businesses, local governments and other school systems, most notably the huge Los Angeles Unified School District last September. The attacks often encrypt data until business or government leaders agree to pay a fee.

In Des Moines, Smith said students will ultimately need to make up the days missed this week.