The latest victim, a 70-year-old man, died at 7:15 a.m. at St. Barnabas Hospital in the Bronx, the New York Post reported. None of the 15 victims has been identified.
The bus had just crossed into the Bronx from Westchester County on Interstate 95 Saturday when it flipped onto its right side and skidded 480 feet into a sign post, which sliced through the vehicle.
Driver Ophadell Williams told police he lost control after a truck clipped the World Wide Tours bus around 5:30 a.m.
Passengers and other witnesses told investigators the bus strayed onto the rumble strips at the edge of the pavement before the accident, a law enforcement official, remaining anonymous, told The New York Times Sunday.
Christopher Hart, vice chairman of the National Transportation Safety Board, said the truck driver was very cooperative. The Post said he contradicted Williams' account.
The Times report said police records show that an Ophadell Williams was convicted of manslaughter in 1992 and served two years in prison. The same man later served four years for larceny.