The bus was hit two times after leaving Deodoro, north of Rio, for Barra Olympic park, southwest in the city. Police searched the bus and said it was stones, not bullets, to break the window, Xinhua news agency reported.
Rio organising committee has confirmed this accident and a special investigation force including the federal police was formed to review it.
Around 12 people were in the bus when this accident occurred. Two of them suffered minor injuries. A journalist from Belarus suffered small cuts on the hand. A volunteer got injured on his arm.
Although police said it was stones hitting the window, passengers on the bus suspected it was small-calibre bullet.
After the incident, all the buses leaving from Deodoro were escorted by the military.