Mumbai, Dec 11 : Four unknown persons barged into a posh building in the Kalbadevi area of south Mumbai and robbed a businessman of Rs 55 lakh after holding him 'hostage' before decamping with the money, police said here on Monday. The daring robbery occurred on Sunday when the businessman was reportedly alone at his home in Aditya Heights building, and the four unidentified men entered his home. They overpowered him, assaulted him, and pushed him into confinement in one of the rooms. Then they broke open a safe and robbed around Rs 55 lakh kept in it before decamping from the spot. The victim later lodged a complaint with LT Marg Police which has launched a probe into the matter that has sparked concerns in several of the quiet localities of south Mumbai. The police are scanning the CCTV footage of the vicinity and launched a manhunt for the unknown robbers, and further details are awaited. /IANS