An elderly Fitchburg couple remained hospitalized Monday morning after the car they were inside of plunged into the Nashua River in Fitchburg. Police Sgt. Mark Jackson said the silver Buick Lacrosse was spotted submerged in 3 feet of water near Barb’s Riverside Café on Westminster Street at about 8:45 a.m. Jackson said a group of nine people, including an off-duty officer, had rushed from the café to try and help the couple, who had been trapped inside the overturned car.