American Water Works said it is in the process of securely reconnecting its systems following a cyberattack discovered on Oct. 3, according to a Thursday regulatory filing.

The largest regulated water utility in the U.S. said there is no evidence the incident impacted its water or wastewater facilities. American Water Works serves more than 14 million people, operating in 14 states and 18 military installations.

The company said its customer portal is again operational and standard billing procedures are back in effect. There will be no late charges during the period when the platform was out of service. 

American Water Works said law enforcement and forensic experts are still investigating the nature and scope of the attack. The company pledged to share any new information when appropriate. 

Moody’s Ratings said it viewed the incident as credit negative, citing the disruption of services across the company’s 14-state operational footprint, in a report issued Thursday. The incident could hurt customer relations and brand reputation, and lead to increased scrutiny from regulators, according to the report.

However, analysts do not expect the incident to have a material impact on the company’s finances as the utility has a $31 billion total asset base and $2.75 billion revolving credit facility.

The Camden, New Jersey-based firm originally disclosed the attack on Monday in a securities filing. The company called the incident unauthorized and immediately disconnected certain systems to prevent further damage.

American Water Works said it takes the cybersecurity of its systems seriously and has taken additional steps to prevent further issues.  

The attack followed months of warnings from federal authorities about hacktivists and state-linked actors targeting water utilities and other critical infrastructure providers that relied on default passwords and failed to implement multifactor authentication. 

The Cybersecurity and Infrastructure Security Agency reiterated those warnings in late September following an attack against a water utility in Kansas.