Twenty-three people have been hurt during Pamplona's running of the bulls.
A Spaniard and an American were gored Saturday by bulls during the run. Many other people were trampled by bulls after they became trapped at an entrance to Pamplona's bull ring.
The animals charged into a tunnel where people were bottled up in the narrow passage.
Early morning bull runs are a major part of the San Fermin festival, which was made famous by Ernest Hemingway's novel The Sun Also Rises.
The number of festival attendees in the northern Spanish city tends to rise on weekends -- increasing the threat of injuries and pileups.
The last fatal goring at a Spanish bull run was in 2009.