Yes I'm guessing: someone dumped multiple piles on BTCE starting at 13:36 my time (11:36 UTC), only a relatively small dump, but stinky nonetheless, causing 25% drop as the orders buried into the book!
Whoever did that could have got more fiat by dribbling in over multiple exchanges.
Here's how it went down...
All charts have same time periods:
Going Down (over 9 minutes)
Going Up (over 14 minutes)
BTCE:Other exchanges only got dented, probably by arbitrage against BTCE:
BITSTAMP:BTC CHINA: