By Kanishka Singh (Reuters) -At least 21 people were injured Monday in an apparent gas leak explosion at the Sandman Hotel in downtown Fort Worth, Texas, the city’s fire department said. Nobody was killed in the explosion and authorities were investigating the cause. Video images from the scene showed rubble in the street between two buildings with first responders on the scene. Craig Trojacek, a spokesman for the Fort Worth Fire Department, said first responders rescued several people trapped in the basement of the hotel. Of the 21 people injured, one person was in critical condition, while f…