CEO Paul McElroy said the JEA website was overwhelmed with hits that forced the utility to take the site down Monday and Tuesday.
"We have a team both externally and internally working on that. The good news is the site was taken down. It's viewed as a denial-of-service attack, so that it may be viewed in non-technical terms as vandalism in terms of overwhelming our site," said McElroy.
The website was back up as of Wednesday morning.
He assured the public that the attack had not compromised any important information.
"There was absolutely no penetration into our system. The electric, water, sewer, financial and customer systems have all been protected. I wanted to publicly apologize for this discomfort and difficulty it has created for our customers who have been trying to reach us through jea.com," said McElroy.
He told JEA' s board of directors Tuesday that teams were working around the clock to have the system operational.
Through Tuesday afternoon, payments through JEA's automatic phone system also were not working. Payments made through autopay, Winn-Dixie, the Tax Collector, JEA's Downtown office and third-party locations all were being processed.
Email sent to JEA was not being received. JEA stop-start orders and reconnect orders are still being processed, but all orders for disconnect for non-pay were suspended until the issue is resolved.
"We know the source is not internal and that it originated in the U.S.," said McElroy.
The investigation is ongoing and includes the efforts of JEA's information technologies, compliance and security divisions and the utility also has hired an outside firm to assist with tracking down the source of the disruption.
Jacksonville Sheriff's Office Public Information Officer Melissa Bujeda said she had not received information on the incident and the Jacksonville office of the Federal Bureau of Investigation did not return calls seeking comment.
JEA reported Tuesday it was experiencing a denial-of-service attack that started at midnight Sunday and led to a shutdown of its website, jea.com, and a loss of internet connectivity for the entire utility.