A firm connected to high net worth investor Dhammika Perera is believed to have taken the stake, dealers said.
Perera is also a major shareholder of PABC bank.
Asian Alliance has posted revenues of 431 million for the six months ended June 2006 and 741 million for 2005.
On Thursday 3.8 million shares of Asian Alliance traded at prices between 20.25 and 21 rupees before closing at 21 rupees up 50 cents.
Meanwhile the broader market closed 0.52 percent with the all share losing 15 points and the Milanka losing 20 points according to provisional data.