An oil and gas pipeline system that was forced to shut down on Friday after a ransomware attack is not expected to be “substantially” restored until the end of the week, its operator, Colonial Pipeline, said on Monday.

“While this situation remains fluid and continues to evolve, the Colonial operations team is executing a plan that involves an incremental process that will facilitate a return to service in a phased approach,” the company said in a statement posted on its website. “This plan is based on a number of factors with safety and compliance driving our operational decisions, and the goal of substantially restoring operational service by the end of the week.”

The company said it was monitoring its customers’ supplies and was working with shippers to move fuel. Oil and gas prices came well off their highs of the day after Colonial’s statement.

The sudden shut down of 5,500 miles of pipeline, which the company says carries nearly half of the East Coast’s fuel supplies, has been a troubling sign of vulnerabilities in the nation’s energy infrastructure.And the shutdown had raised concerns about fuel supplies to large portions of the country. Prices on gasoline futures had soared on Monday as a result, and analysts had said a prolonged shutdown could drive them even higher — potentially affecting prices consumers pay for gas at the pump.Experts said several airports that depend on the pipeline for jet fuel, including those in Nashville, Baltimore-Washington and Charlotte and Raleigh-Durham, N.C., could have a hard time later in the week. Airports generally store enough jet fuel for three to five days of operations.

This is a developing story. Check back for updates.