The Lansing, Mich., Board of Water & Light (BWL) expects to be fully back online today after suffering a cyberattack earlier this week that knocked the utility's internal computer systems offline.

The attack took place late on April 25 when an employee opened an email and clicked on a malicious attachment, one that quickly began encrypting the organization's files, according to the Lansing State Journal. BWL had to shut down its accounting and email service for its 250 BWL employees and suspend some field work until the problem could be rectified. However, its 96,000 customers did not lose power and BWL said all customer account data remained secure, the State Journal reported.

BWL officials did not say if they received a ransom demand, as malware that encrypts files is generally a sign of a ransomware attack, but the Federal Bureau of Investigation and local law enforcement are involved.