A cyber-criminal gang that took a major US fuel pipeline offline over the weekend has acknowledged the incident in a public statement. "Our goal is to make money and not creating problems for society," DarkSide wrote on its website.The US issued emergency legislation on Sunday after Colonial Pipeline was hit by a ransomware cyber-attack. The pipeline carries 2.5 million barrels a day - 45% of the East Coast's supply of diesel, petrol and jet fuel. The operator took itself offline on Friday after the cyber-attack. Work to restore service is continuing. On Monday, the FBI officially confirmed that DarkSide was responsible for compromising Colonial Pipeline's networks, saying that it was continuing to work with the firm and other government agencies on the investigation. During a speech about the economy at the White House on Monday, US President Joe Biden said that he was being "personally briefed" on the situation with the pipeline each day. "The agencies across the government have acted quickly to mitigate any impact on our fuel supply," he said. "We're prepared to take additional steps depending on how quickly the company is able to bring its pipeline back up to capacity." A number of cyber-security researchers, including firms contacted by the BBC, have speculated that the cyber-criminal gang could be Russian, as their software avoids encrypting any computer systems where the language is set as Russian. Mr Biden said that the US government was concerned about this aspect of the cyber-attack. "I'm gonna be meeting with President Putin and so far there is no evidence, based on our intelligence people, that Russia is involved," he said. "Although, there's evidence that the actors' ransomware is in Russia - they have some responsibility to deal with this." DarkSide posted a statement on its website on Monday, describing itself as "apolitical". "We do not participate in geopolitics, do not need to tie us with a defined government and look for... our motives," the group said. The group also indicated it had not been aware that Colonial was being targeted by one of its affiliates, saying: "From today, we introduce moderation and check each company that our partners want to encrypt to avoid social consequences in the future."