A 'Jose Escolar Gil' ranch fighting bull runs with his horn stained with blood after goring a reveler during the daily morning running of the bulls of the San Fermin festival in Pamplona, Spain, Saturday, July 11, 2015. Revelers from around the world arrive in Pamplona every year to take part on some of the eight days of party and the running of the bulls. (AP Photo/Daniel Ochoa de Olza)

PAMPLONA, Spain - One bull chosen to take part in Saturday's San Fermin festival took one look at thousands of thrill-seekers waiting to be chased down Pamplona's narrow streets and scampered back to the safety of his corral.

In a scene that confounded revelers and experts — and could have been scripted by Munro Leaf, who wrote "The Story of Ferdinand" — a reticent bull named Curioso I barely ran 20 yards (meters) before heading back.

Meanwhile, his five ornery stable-mates gored four revelers — including one 20-year-old American identified only by his initials A.G.O. — and injured five others with cuts and bruises as they hurtled through the northern Spanish city.

One bull charged into runners, goring one deeply in a thigh while cutting another runner's leg as it lifted its head.

Red Cross spokesman Jose Aldaba said four people received treatment after being gored while at least five others were recovering from bruises.

Kiko Betelu of the region of Navarra's medical service said three of the gorings were simple to treat but one of the injuries was deep and required surgery.

Normally six bulls run in the San Fermin festival, but on this occasion Curioso — a 1,180 pound (535 kilogram) beast belonging to the Jose Escolar breeding ranch — later had to be transported to the ring to join the other five.

Unlike the gentle, flower-sniffing Ferdinand, Curioso almost certainly won't get a chance to retire.

According to San Fermin experts commenting for state television TVE, the last time a bull turned back to the holding pen was in the 19th century.

The run covers 930-yards (850-meters) from a holding pen on the edge of town to the central bullring where the beasts — including Curioso — face matadors and almost certain death in afternoon bullfights.

The cobblestone streets of Pamplona were packed with thrill-seekers who had travelled to the northern city to take part in the annual San Fermin festivities. The weekend runs are traditionally the most popular and well-attended.

The nine-day fiesta was immortalized in Ernest Hemingway's 1926 novel "The Sun Also Rises."

Every morning of the festival at 8 a.m., the bulls race through the medieval streets accompanied by an equal number of large steers — each wearing a clanking cowbell — tasked with keeping the pack tight and galloping at an even pace.

This was the first time that breeder Escolar — whose heaviest animal was the 1,280 pound (580 kilogram) Costurero — had presented bulls for this festival that dates back to the late 16th century.

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Heckle reported from Madrid.

News from © The Associated Press, 2015