A major U.S. fuel pipeline remains largely shut down Monday after a cyberattack caused service to be suspended. The incident, reported Friday, led to the shutdown of a main fuel line operated by Colonial Pipeline, a company based in Georgia. The pipeline carries gasoline and other fuel from Texas to the U.S. Northeast. The company says it supplies about 45 percent of all the fuel used on the U.S. East Coast. Some are considering the cyberattack the most damaging so far against important U.S. infrastructure. Colonial said Monday it hopes to have most of its fuel transportation system running again by the end of the week. The company is in the process of restarting its network, which transports over 2.5 million barrels of gasoline, diesel and jet fuel each day. The company says it was hit by a ransomware attack. In such attacks, online attackers infect the computer systems of organizations and hijack information in a way that leaves it unreadable. The attacker then demands payment in exchange for returning the information to a readable state. Law enforcement agencies are investigating the incident. The Federal Bureau of Investigation (FBI) said Monday the attack was carried out by a criminal group known as DarkSide. A news release issued Monday in the name of DarkSide stated its purpose, but did not name Colonial Pipeline, Reuters news agency reported. “Our goal is to make money, and not creating problems for society,” the group said. Cybersecurity experts who have studied DarkSide say the group appears to be made up of experienced cybercriminals who aim to get as much money as they can from their targets. They're very new but they're very organized, said Lior Div, chief of Cybereason, a security company based in Boston. DarkSide claims it does not attack hospitals, nursing homes or educational or government targets. It says it donates part of the money it receives to charity.