Thirteen people have been injured during the opening of the annual bull-running festival in Pamplona, northern Spain.
The Red Cross said the injuries were mostly cuts and bruises suffered by people falling over or getting trampled by one of the six bulls set loose.
But one man suffered a collapsed lung, ruptured spleen and broken ribs.
Meanwhile, police said a man who died after falling from the city's walls on Sunday was a 23-year-old from Ireland.
During the nine-day festival, up to six bulls and a number of steers are released at 0800 (0600 GMT) from a pen into a closed-off street.
They then run 825m (2,700ft) to the bullring, where they face matadors later in the day.
Ahead of them are the runners, who try to stay as close to the bulls as possible without falling or being gored.
Monday's run took just over four minutes, organisers said, which is slow compared to previous years.
The sprint through the cobbled streets turned chaotic after the pack of half-tonne animals became separated after ploughing into a crowd of people.
Several of the injured were foreign tourists, according to the Red Cross.
The festival, which has been held since 1591, was made internationally popular by Ernest Hemingway's 1926 novel, The Sun Also Rises.
Fourteen people have been killed since record-keeping began in 1924.
It has been the target of protests by animal rights protesters, who say bull-running is cruel.
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