Fuel holding tanks are seen at Colonial Pipeline's Dorsey Junction Station in Woodbine, Maryland on May 13, 2021.

Colonial Pipeline, the US oil conduit shut down for days by a cyber attack earlier this month, said on Tuesday a server had been disrupted but deliveries of petroleum products were not affected.

The largest fuel conduit system in the United States that sends gasoline and jet fuel from the Gulf Coast of Texas through the east coast shut down its network on May 7 after a ransomware attack.

Colonial last Thursday announced it had restarted its entire network and resumed fuel deliveries to all markets, but in a statement Tuesday said its systems had again been disrupted as they recover from the attack.

"Our internal server that runs our nomination system experienced intermittent disruptions this morning due to some of the hardening efforts that are ongoing and part of our restoration process," a Colonial spokesperson said.

"These issues were not related to the ransomware or any type of reinfection," the spokesperson said, adding, "The Colonial Pipeline system continues to deliver refined products as nominated by our shippers."

The pipeline's shutdown caused panic buying in the eastern United States and a spike in gasoline prices as Washington waived clean air regulations and rules on shipping and trucking to alleviate shortages.

Unknown actors last Friday shut down the servers of Darkside, which was behind the ransomware scam, amid reports Colonial paid the Russia-based cyber-extortionist millions of dollars in bitcoin.