A gang of fraudsters tricked the Olympic Delivery Authority (ODA) out of £2.3 million, a court heard.
The conmen contacted the ODA, which is responsible for planning and building venues and Games-related infrastructure, pretending to work for construction firm Skanska.
The ODA was told that the company, which has worked on numerous projects for the 2012 Games, was changing its bank account details and that all future payments should be made to the new account.
The authority then made a payment of £2.3 million into the account, which was in fact held by ringleader Ansumana Kamara.
After the money was paid, Kamara then made a series of rapid transactions to try to cover his tracks, prosecutor James Dawes said.
Kamara, who has previously appeared before the courts in relation to the matter, also put money into accomplices' accounts before attempting to wire a cheque for £2 million to Nigeria.
Eight co-conspirators, who are standing trial at Southwark Crown Court, then laundered the cash, it is alleged.
"People involved in money laundering take great effort to try and disguise the money trail," said Mr Dawes.
"This case relates to what they tried to do with the £2 million to try and break the money trail.
"It involved taking it out in cash, but the plan was to break the trail by other means to send the money out of the country to Nigeria."