AUGUSTA, Maine — Augusta City Center, which hosts municipal offices, has been closed since a cyber attack on Thursday.

City officials say that a ransomware virus got onto computer systems on April 18 and trapped almost all data.

No data has been deleted or stolen, but all computers are locked up, making it impossible to perform daily functions like vehicle registration.

Police and fire services and Augusta's school system were not affected by the virus, according to officials. 

Chief of the Augusta Police Department Jared Mills says city offices will likely reopen on Monday.

"We're very optimistic that will be the case," said Mills. "Obviously, we're at the mercy of backups and putting things back on the servers -- and that type of thing and that only works as fast as the computer programs do."

The Augusta Police Department, as well as state agencies and the FBI, are investigating how the attack began.