We now know who blew the whistle on the Visium hedge fund fraud

The whistleblower behind the investigation into Visium Asset Management, the one-time $8 billion hedge fund that is shuttering amid fraud charges, has been revealed.

A former trader at the firm, Jason Thorell, approached the government, according to a Bloomberg News report out Monday morning.

He worked at Visium from 2011 to 2013, according to a LinkedIn page. He couldn't immediately be reached for comment.

Here's more from the Bloomberg report by Christian Berthelsen, Matt Robinson and Katia Porzecanksi:

"Thorell's approach to the government triggered an investigation into how Visium valued holdings in its credit portfolio, a probe that expanded into charges that executives were trading on inside tips about pending regulatory decisions about certain drugs. He is one of at least four people cooperating with a continuing U.S. investigation."

Thorell participated in the scheme to misvalue credit securities, according to court filings which left him unnamed.

A broker who helped Visium in its alleged fraud by providing price quotes, David "Scott" Vandersnow, is also helping the government, according to Bloomberg. He couldn't immediately be reached for comment.

The credit fraud charges are among others that Visium is facing from the government, namely insider trading in its flagship healthcare fund from 2005 through 2011.

Visium spokesman Jonathan Gasthalter declined to comment.

To read the full Bloomberg story, click here.