(Adds detail on restart, energy secretary tweet)

NEW YORK, May 12 (Reuters) - Colonial Pipeline, operator of the nation's largest fuel pipeline network, has begun the process of restarting its service to the East Coast after a six-day shutdown, a company spokeswoman said on Wednesday.

The system transports more than 2.5 million barrels per day of gasoline, diesel and jet fuel from the U.S. Gulf Coast to the Southeast and East Coast. The restart follows a ransomware hacking attack on the company.

Following the restart, it will take several days for the fuel delivery supply chain to return to normal, Colonial said in a news release. Some markets served by Colonial may experience, or continue to experience, intermittent service interruptions during the startup period.

The pipeline operator's chief executive agreed to begin turning systems controlling the 5,500-mile-long (8,850-km) fuel pipe back on at about 5 p.m., Energy Secretary Jennifer Granholm wrote on Twitter.

(Reporting by Joseph Menn and Stephanie Kelly; Editing by Chris Reese and Peter Cooney)