Colonial Pipeline, which operates the largest refined-products pipeline in the US, said that a cyberattack on May 8 forced it to shut down its entire network. The Georgia-based company delivers 45 percent of all the fuel consumed on the East Coast via a pipeline from Houston, TX to New Jersey.

“At this time, our primary focus is the safe and efficient restoration of our service and our efforts to return to normal operation,” the company said in a statement on Friday. “This process is already underway, and we are working diligently to address this matter and to minimize disruption to our customers and those who rely on Colonial Pipeline.”

While some reports have suggested that this was a ransomware attack – a form of cyber-extortion – a motive has yet to be established.

The incident highlights the potential vulnerability of crucial systems in the U.S. “The attacks were extremely sophisticated and they were able to defeat some pretty sophisticated security controls,” said Mike Chapple, an IT professor at the University of Notre Dame and former National Security Agency scientist, “or the right degree of security controls weren’t in place,”