Washington has expelled two Cuban diplomats after US embassy staff in Havana suffered mysterious physical symptoms.<br/><br/>It was not immediately clear what had happened, with spokeswoman Heather Nauert saying there were no "definitive answers about the source or cause". Meanwhile, Cuba's foreign ministry has said it was investigating the allegations. <br/><br/>It called the expulsion of its staff unjustified but said it was willing to co-operate with Washington to clarify what had happened. <br/><br/>The Ministry said, Cuba has never, nor would ever, allow the Cuban territory to be used for any kind of action against accredited diplomats or their families.