WASHINGTON - After a six-day distribution pinch that prompted panic at the gasoline pumps in parts of the country, fuel is flowing again through the most important U.S. East Coast pipeline which was crippled by a ransomware attack blamed on Russian hackers.

"Don't panic," U.S. President Joe Biden appealed to motorists on Thursday. "This is a temporary situation. Don't get more gas than you need in the next few days."

The president also warned gas station operators not to engage in price gouging.

FILE - A customer helps pump gas at Costco, as others wait in line, in Charlotte, N.C., May 11, 2021.

"Do not try to take advantage of consumers during this time," he said in remarks from the Roosevelt Room of the White House. "Nobody should be trying to use this situation for financial gain."

Colonial Pipeline "has made substantial progress in safely restarting our pipeline system and can report that product delivery has commenced in a majority of the markets we service," the company said in a Thursday morning statement. "By midday today, we project that each market we service will be receiving product from our system."

The 8,850-kilometer-long pipeline carries about 380 million liters per day of gasoline, diesel and jet fuel.

Due to the pipeline's length, "we'll not feel the effects at the pump immediately. This is not like flicking on a light switch," said Biden in his midday Thursday remarks.

FILE - A man loads 5-gallon gasoline tanks in his car at a Wawa gas station, in Tampa, Florida, May 12, 2021.

Colonial Pipeline paid nearly $5 million to hackers last Friday, according to Bloomberg News, which said that in exchange for the ransom in cryptocurrency the company received a tool to decrypt its scrambled files, which did not work.

The company has not commented on whether it paid the ransom.

"I have no comment on that," replied Biden when asked by a reporter on Thursday whether he had been briefed about any ransom payment.

"I have no knowledge of whether a ransom was paid," said Brandon Wales, acting director of the Cybersecurity and Infrastructure Security Agency.

Biden, in response to reporters' questions following his prepared remarks, said that according to a Federal Bureau of Investigation report Russian President Vladimir Putin or the Russian government were not involved in the malware attack on Colonial Pipeline.

FILE - Tanker trucks are parked near the entrance of Colonial Pipeline Company, May 12, 2021, in Charlotte, N.C.

Noting that "criminal hackers" have been able to disrupt infrastructure, Biden said the United States needs to modernize and secure key sectors in order to effectively compete with China this century.

"The likelihood is increasing almost every day" for a catastrophic-level cybersecurity incident, Wales told a group of defense writers on Thursday. "We're seeing the prelude to that today."

Concerning ransomware hacks similar to the one that crippled the pipeline, Wales said, "This is a scourge that is not going to be easily eradicated.

Wales praised an executive order Biden signed on Tuesday hardening the federal government's responses to cybersecurity incidents. The CISA official said, beyond that, "we need Congress to take certain actions" to require private industry to notify government authorities of cyberattacks.

FILE - Homeland Security Secretary Alejandro Mayorkas speaks during a press briefing at the White House, March 1, 2021.

To ease fuel supply constraints, Homeland Security Secretary Alejandro Mayorkas on Wednesday evening signed a rare waiver to the Jones Act, allowing non-U.S. ships to transport fuel between American ports.

"In the interest of national defense, I have approved a temporary and targeted waiver request to an individual company," explained Mayorkas in a statement. "This waiver will help provide for the transport of oil products between the Gulf Coast and East Coast ports to ease oil supply constraints as a result of the interruptions in the operations of the Colonial Pipeline."