http://wolfstreet.com/2015/06/08/is-this-why-u-s-treasuries-are-diving/

"Over the last few years, any illusions we might have nurtured that our financial markets are fair have been destroyed piece by piece by a relentless and consistent series of scandals: Libor rates, precious metals, stocks, commodities, foreign currencies…. They were all caught up in massive manipulation schemes.....

 But there was one market that folks thought was somehow above this endless sea of manipulation, and so they have confidently placed their bets, including foreign governments, thinking – nay, deluding themselves into thinking – that this market was one of the last ones to be fair: the US Treasury market....


So how tempting would it be to manipulate this monster market? Very, apparently.
Turns out, the Department of Justice smells a rat in this until now pristine Treasury market, according to the New York Post:

Justice lawyers, believed to be in the early stages of a probe, have reached out in recent months to at least three of the 22 banks that act as primary government debt dealers and requested information regarding auctions of Treasury debt, said one person close to one of the banks that received the request.
No single bank has become the focus of the probe, it is believed, and no bank has been accused of any wrongdoing. In addition, there is no guarantee that the requests for information will turn up any evidence of manipulating Treasury auctions.
A spokesman for the DOJ on Sunday declined comment on the matter."