The F.B.I. on Monday confirmed that DarkSide, a hacking group, was responsible for the ransomware attack that closed a U.S. pipeline that provides the East Coast with nearly half of its gasoline and jet fuel.

The confirmation of the hack, which prompted emergency White House meetings over the weekend, comes as the Biden administration in the coming days is expected to announce an executive order to strengthen America’s cyberdefense infrastructure.

Colonial Pipeline, the operator of the system, issued a statement on Monday saying that restoring service “takes time.” They added that while this situation “remains fluid and continues to evolve” the company will restore service incrementally, with the goal of “substantially” restoring service by the end of the week.

Late Friday, Colonial said in a vaguely worded statement that it had shut down its 5,500 miles of pipeline, which it says carries 45 percent of the East Coast’s fuel supplies, in an effort to contain the breach. Earlier in the day, there had been disruptions along the pipeline, but it was not clear at the time whether that was a direct result of the attack or of the company’s moves to proactively halt it.

Energy analysts warned that a prolonged suspension of an oil pipeline could raise prices at the pump along the East Coast and leave some smaller airports scrambling for jet fuel.