A would-be underwear bomber" involved in a plot to attack a US-based jet was in fact working as an undercover informer with Saudi intelligence and the CIA, it has emerged. The revelation is the latest twist in an increasingly bizarre story about the disruption of an apparent attempt by al-Qaida to strike at a high-profile American target using a sophisticated device hidden in the clothing of an attacker. The news that the individual at the heart of the bomb plot was in fact an informer for US intelligence is likely to raise just as many questions as it answers. Citing US and Yemeni officials, Associated Press reported that the unnamed informant was working under cover for the Saudis and the CIA when he was given the bomb, which was of a new non-metallic type aimed at getting past airport security. The informant then turned the device over to his handlers and has left Yemen, the officials told the news agency.