CHENNAI: Police have launched a hunt for an unidentified man who robbed cash worth Rs 40,000 from a woman by threatening her with a knife at Teynampet on Sunday evening. The masked man had allegedly poured petrol on Punitha (40) and then threatened her. Punitha works with a SHG in the city. Police investigations revealed that Punitha had collected Rs 92,000 from SHG workers and was counting the money outside her home when the incident happened. Police suspect that the man knew Punitha and had been observing her. After apprehending her, he took Rs 40,000 from her hand, leaving the rest in the bag. Punitha filed a complaint with Teynampet police, who have registered a case and are investigating.