This is what I love about bitcoin and the cryptospace. There are more plot twists than my favorite tv show Game of Thrones.
How did they prove that the stolen bitcoins from MtGox were laundered in BTCe? What bitcoin mixers were used to hide their transactions? Is it also connected to the closure of Bitmixer?
I suggest you read here mate:
http://blog.wizsec.jp/2017/07/breaking-open-mtgox-1.html?m=1WizSec (bitcoin security specialists) conducted a private independent investigation the largest Bitcoin theft - MtGox collapse. They have put up a through investigation and follow the trail linking BTc-e owner Alexander Vinnik with the hack coins in Mt. Gox:
- In September 2011, the MtGox hot wallet private keys were stolen
- Over time, the hacker regularly emptied out whatever coins they could spend using the compromised keys, and sent them to wallet(s) controlled by Vinnik.
- By mid 2013 when the funds spendable from the compromised keys had slowed to a near halt, the thief had taken out about 630,000 BTC from MtGox
- After the coins entered Vinnik's wallets, most were moved to BTC-e and presumably sold off or laundered (BTC-e money codes were a popular choice). In total some 300,000 BTC ended up on BTC-e, while other coins were deposited to other exchanges, including MtGox itself.
- Some of the funds moved to BTC-e seem to have moved straight to internal storage rather than customer deposit addresses, hinting at a relationship between Vinnik and BTC-e.
- Moving coins back onto MtGox was what let they identify Vinnik, as the MtGox accounts he used could be linked to his online identity "WME". As WME, Vinnik had previously made a public outcry that coins had been confiscated from him (the coins in question coming from Bitcoinica).
Regarding the Bitmixer, it didn't mentioned about a mixing services being involved in laundering the money. We can only speculate that the closure of Bitmixer.io was just a coincidence, otherwise, if new development will come out linking them to the crimes.