One participant was gored in the face and 12 others sustained injuries during a chaotic bull run at Spain's San Fermin festival on Saturday.

The six bulls and accompanying steers charged through packed crowds along the narrow street course in Pamplona. The large animals knocked runners to the cobblestones, and stumbling participants caused several pileups during the roughly two-and-a-half-minute run.

The University of Navarra Hospital reported that 12 people required medical treatment for various knocks and injuries. One black bull broke away from the pack early in the 875-meter course and ran into a group of people, striking one individual in the face with its horn. It was not immediately clear if this was the moment of the goring.

This year's festival marks the 100th anniversary of Ernest Hemingway's novel 'The Sun Also Rises,' which contributed to the San Fermin festival's international renown. The last fatality in the festival's bull runs occurred in 2009, though gorings and broken bones are common occurrences, partly attributed to the presence of many novice runners and foreign tourists alongside experienced locals.

Thousands of international visitors attend the week-long festival annually, participating in the renowned encierros where bulls are released at 8 a.m. to race from their corral to the bullring along an 850-meter route through the city's old town. British nationals typically constitute about 4% of international participants.

Runners aim to stay as close to the bulls as possible without falling or being gored. The festival also includes parades, music, religious ceremonies, and continuous street festivities.

The six bulls and accompanying steers charged through crowds of thrill-seekers who packed the narrow street course in Pamplona

Earlier in the week, at least three people were hospitalized on the first official day of the festival. Among them were a 61-year-old American with a head injury, and two Spaniards aged 20 and 34, who sustained leg and ankle injuries respectively. Medical staff treated a fourth individual at the scene, and a fifth received medical attention but was not expected to require hospitalization, with no gorings reported on that day.

One runner was pierced by a horn in the face, while 12 more people needed medical treatment for an assortment of knocks, according to the University of Navarra Hospital

The huge 600kg animals knocked bodies to the cobblestones, and stumbling runners caused several pileups during the two-and-a-half-minute run from the pen to the bull ring where bullfighters will kill the bulls later in the day