American officials say the Nigerian man accused of trying to blow up a US plane over Detroit on Christmas Day is now cooperating with the authorities and providing useful information.Law enforcement officials said Umar Farouk Abdulmutallab was providing, what they called, useful, current and actionable intelligence.He had stopped talking to investigators but started again last week. Abdulmutallab, 23, is accused of trying to blow up a flight to Detroit with a bomb hidden in his underwear. He has denied a charge of attempting to murder 290 people.