Water supplier American Water Works says the system was hacked

American Water Works — a provider of drinking water and wastewater services to more than 14 million people — said Monday that hackers had breached its computer network and systems, prompting it to stop billing customers.

The Camden, New Jersey-based utility became aware of the unauthorized activity Thursday and took protective measures, including shutting down some systems, American Water Works said in a regulatory filing. The company does not believe its facilities or operations have been affected by the cybersecurity incident, but is “currently unable to predict the full impact,” it said.

“In an effort to protect our customers' data and prevent further damage to our environment, we have disconnected or disabled some systems. Customers will not be charged any downtime while these systems are unavailable,” an American Water spokesperson told CBS News via email. A round-the-clock investigation is underway to investigate the nature and scope of the incident,” the spokesperson added.

The company said it has notified law enforcement and is cooperating with them.

According to its website, American Water is the largest regulated water and wastewater utility company in the United States, and provides drinking water and wastewater service to more than 14 million people in 14 states and 18 military installations. It operates more than 500 water and wastewater systems serving nearly 1,700 communities in California, Georgia, Hawaii, Illinois, Indiana, Iowa, Kentucky, Maryland, Missouri, New Jersey, Pennsylvania, Tennessee, Virginia and West Virginia.

The company's shares lost $5.58, or 3.9%, to close at $136.99, leaving it with a market capitalization of $26.69 billion.

U.S. officials have recently become concerned about alleged efforts by Chinese intelligence officials to breach critical U.S. infrastructure networks such as water-treatment facilities and a cyber attack targeting U.S. broadband providers in Beijing, the Wall Street Journal reported Friday night, citing people familiar with the matter.