It was a thriller made way back in 1988 starring Malayalam superstar Mammootty. Now �Oru CBI Dairy Kurippu director K. Madhu is working on its fourth sequel. In a chat, Madhu said scripting work is going on and the film would be released next year. �To the best of my knowledge this is certainly unique, with not a single film going into four sequels. And mind you, each of the earlier released films were superhits,� said Madhu. The first sequel was �Jagratha� in 1989 , �Sethurama Iyer CBI� in 2004 and �Nerariyan CBI� in 2005. �Another uniqueness of this film is that the director, scriptwriter (S.N. Swamy), music (Shyam) and leader actor Mammootty have been the same in all the four films and will continue in the fifth one as well,� pointed out Madhu. Each of the films saw Mammootty playing the role of a Central Bureau of Investigation (CBI) officer who along with his team solves a crime when the local police fails. �This time also the plot is the same but the name of the film is not ready. By all means viewers will certainly not be let down and can expect another thriller,� said Madhu who made his directorial debut in 1986 and so far has done 28 films.