The 400-year-old tradition takes place each morning over eight days during the San Fermin festival in Pamplona in northern Spain. The festival runs from July 6 to July 14. The bull run -- known as the "encierro" -- started on July 7.
The Red Cross in Navarra said five people were taken to hospitals in the first running on Saturday and four people were taken in the second running on Sunday. The extent of injuries was not immediately available.
Reuters reported that one person was gored during the opening day of the bull run.
The Red Cross said it assisted nearly 100 people over the two runs.
Injuries are common during the bull run. Between 1910 and 2014, 15 people have died from gorings.
Traditionally, the bull run was used as a way of getting the bulls from the city outskirts to the bull ring.
After the launching of two rockets, the bulls charge behind amateur daredevils, many dressed in traditional white attire with dashes of red, for 825 meters (half a mile) which is the distance between the corral and the bull ring, according to the festival website.
The morning runs through the pavement of the old town streets last between three and 10 minutes.
The event ends with an evening bullfight, during which the bulls are eventually killed by matadors.
The bull run is the marque event of the fiesta celebrated in honor of San Fermin, patron saint of Navarra. Other activities include concerts and parades. The weekends of the fiesta traditionally draw the largest crowds, tripling Pamplona's population of about 200,000.
In recent years, animal rights groups have criticized the event for its treatment of the bulls.
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