At least 11 people were killed and 40 others injured in a stampede triggered by tear gas firing by police at a religious service in a stadium in Zimbabwe, media reported Friday.The stampede occurred in the Mbizo stadium of Kwekwe town as some 15,000 worshippers rushed to leave the service which was being led by a popular local preacher.Police had left only one exit open and blocked the rest, so some tried to break off parts of the wall to exit the stadium.Police then fired tear gas in a bid to disperse them, causing a stampede that left at least 11 dead.Security forces have confirmed the incident, but have not provided any justifications for the action.