Over 30 UBS employees and senior managers are reported to be implicated in the alleged manipulation of Libor, while the estimation of the settlement has risen to $1.5bn.
According to a report in the Financial Times, citing unnamed sources, dozens of UBS bankers and senior managers are involved in the investigation over the rigging of one of the world's most important interbank lending rates, but not all will face civil or criminal charges as the "level of alleged misconduct varies among them."
UBS is also tipped to be finalising a deal with US, UK and Swiss authorities this week and will pay close to $1.5bn (£926m; €1.1bn), which is three times the initial estimates of $450m.
Reports from the FT and Reuters say that while its Japanese securities subsidiary will plead guilty to a US criminal offence, the "bank will not lose its ability to conduct business in Japan".
Details of the settlement with the US' Commodity Futures Trading Commission (CFTC), US Department of Justice (DoJ), UK's Financial Services Authority and UBS's main Swiss supervisor Finma, are expected to be published Wednesday. The agreement would mark the completion of a libor-related settlement with regulators.
UBS declined to comment on when contacted by IBTimes UK.
In June this year, Barclays settled a record fine of £290m with the same US and UK authorities for manipulating Libor, which resulted in the resignation of a number of senior executives, including its chairman, CEO and COO and a raft of UK Treasury Select Committee meetings.
In 2011, UBS had its bank's operations suspended in Japan, after the country's regulator, the Securities and Exchange Surveillance Commission (SESC), found that some staff attempted to manipulate Tokyo interbank offered rates (Tibor).
UBS later revealed in its penultimate quarterly report that it had reached immunity deals with the DoJ and regulators in Switzerland and Canada, giving it protection against enforcement action in relation to certain transactions and submissions for Yen Libor and Euroyen Tibor.
"UBS has been granted conditional leniency or conditional immunity from authorities in certain jurisdictions, including the Antitrust Division of the DoJ and the Swiss Competition Commission (WEKO), in connection with potential antitrust or competition law violations related to submissions for Yen Libor and Euroyen Tibor," it says in the report.
"WEKO has also granted UBS conditional immunity in connection with potential competition law violations related to submissions for Swiss franc Libor and certain transactions related to Swiss franc Libor. The Canadian Competition Bureau has granted UBS conditional immunity in connection with potential competition law violations related to submissions for Yen Libor. As a result of these conditional grants, we will not be subject to prosecutions, fines or other sanctions for antitrust or competition law violations in the jurisdictions where we have conditional immunity or leniency in connection with the matters we reported to those authorities, subject to our continuing cooperation," adds the statement.