It was about 4 in the afternoon (1.30am IST on Thursday) on Wednesday on the East Coast of the US when chaos struck online.

Dozens of the biggest names in America — including Joseph R. Biden Jr, Barack Obama, Kanye West, Bill Gates and Elon Musk — posted similar messages on Twitter: Send Bitcoin and the famous people would send back double your money.

It was all a scam, of course, the result of one of the most brazen online attacks in memory.

A first wave of attacks hit the Twitter accounts of prominent cryptocurrency leaders and companies. But soon after, the list of victims broadened to include a Who’s Who of Americans in politics, entertainment and tech, in a major show of force by the hackers.

Twitter quickly removed many of the messages, but in some cases similar tweets were sent again from the same accounts, suggesting that Twitter was powerless to regain control.

The company eventually disabled broad swathes of its service, including the ability of verified users to tweet, for a couple of hours as it scrambled to prevent the scam from spreading further. The company sent a tweet saying that it was investigating the problem and looking for a fix. “You may be unable to Tweet or reset your password while we review and address this incident,” the company said in a second tweet. Service was restored around 8.30 Wednesday night (6am IST on Thursday).

Twitter’s investigation into the breach revealed that several employees who had access to internal systems had their accounts compromised in a “coordinated social engineering attack”, a spokesman said, referring to attacks that trick people into giving up their credentials. The attackers then used Twitter’s internal systems to tweet from high-profile accounts like Biden’s.

“We’re looking into what other malicious activity they may have conducted or information they may have accessed,” Twitter’s spokesman added.

“We’ve taken significant steps to limit access to internal systems and tools while our investigation is ongoing.”

Jack Dorsey, Twitter’s chief executive, said in a post on Wednesday night that it was a “tough day for us at Twitter. We all feel terrible this happened. We’re diagnosing and will share everything we can when we have a more complete understanding of exactly what happened.”