A devastating cyberattack has forced U.S. fuel pipeline operator Colonial Pipeline to shut down its entire network of 8851-km of pipelines, the company said over the weekend.

Colonial's network supplies fuel from U.S refiners on the Gulf Coast to the populous eastern and southern United States. The company transports 2.5 million barrels per day of gasoline, diesel, jet fuel and other refined products through its extensive system, amounting to some 45 percent of the East Coast fuel supply.

"We have since determined that this incident involves ransomware," Colonial Pipeline said. "In response, we proactively took certain systems offline to contain the threat, which has temporarily halted all pipeline operations, and affected some of our IT systems."

Former cyber officials suspect that a criminal gang called the "Dark Side" and emanating from Russia is behind the attack. The incident has led the White House to form an interagency working group over the weekend to prepare for various scenarios, including whether additional steps need to be taken to mitigate any potential impact on fuel supply, a White House official said Sunday.

Prices at the pump are not expected to rise unless the outage lasts more than three days, experts say. But if it ends up being a long-term shutdown the impact could be significant given the size of the line.

"The challenges brought on by the Colonial Pipeline shutdown would only develop after a few days of outage," said Patrick DeHaan, head of petroleum analysis at GasBuddy. He warned drivers against panic buying. "What could make a temporary pipeline shutdown much worse is if Americans wrongly fear shortages," he said. The American Automobile Association said "The shutdown can have a large impact if it is prolonged."