(Reuters) - Atlanta took down its water department website indefinitely on Thursday, two weeks after a ransomware cyber attack tore through the city’s computer systems in one of the most disruptive hacks ever to strike a U.S. local government.

A view of Atlanta's City Hall, in Atlanta, Georgia, U.S. March 31, 2018. REUTERS/Laila Kearney

“The Department of Watershed Management’s website ... will be offline for server maintenance and updates until further notice,” the City of Atlanta wrote on Twitter.

Atlanta’s watershed department was among the operations hard-hit by the March 23 attack that continues to block access to databases, postpone municipal court dates and stifle the city’s ability to collect some payments for public services.

Employees with the water department said they were unable to turn on their work computers or gain wireless internet access for roughly a week after the attack, but they were instructed to report to their offices at City Hall anyway.

Many of the department’s systems have lumbered back to life in recent days, but there is still disruption, said one employee, who asked not to be identified.

“There’s definitely work not being done and there’s definitely bills not being able to be paid,” the employee said.

Hackers used a potent computer virus known as SamSam to encrypt large swaths of city data in the attack and demanded a payment of six bitcoins, worth $51,000 at the time, to release the information.

Atlanta Mayor Keisha Lance Bottoms, who took office in January, has declined to say whether the city was negotiating with the hackers.

City officials have not disclosed the extent to which its computer backup systems were corrupted or what type of data is unable to be recovered without paying the ransom.

A federal criminal investigation into the breach is under way.