Twenty-three runners were treated for injuries here Saturday after the seventh running of the bulls at Spain's San Fermin festival, where a pile-up of people at the entrance to the ring made for a dangerous conclusion to the run.

A 19-year-old Spaniard sustained very serious injuries after being trapped in the stampede, suffering a crushed thorax and having to be connected to a respirator.

The run turned especially dangerous when a human wall formed near the ring and the bulls from the Fuente Ymbro ranch charged at the people stuck in the pile-up.

Experts were forced to intervene and lead the herd into the ring by an alternate passageway.

More people were injured Saturday than in the first five runs of this year's festival combined.

Three people were gored on Friday, ending a record streak of five days without any runners being pierced by horns.

The San Fermin festival, which began on July 6 and ends on Sunday, when the last of eight running of the bulls will take place, is known around the world for its bull runs and uninhibited street revelry.

Pamplona, a normally quiet town, welcomes hundreds of thousands of Spanish and international visitors annually during the festival, which was first held about 400 years ago and was popularized by Ernest Hemingway in his 1926 novel "The Sun Also Rises."

Besides the bull runs, hundreds of events have been scheduled for this year's edition of San Fermin.

The run through the medieval streets of Pamplona's historic center, usually lasting four minutes, is especially dangerous because some runners take part in the event after all-night drinking binges.

This makes runners reckless and more likely to get too close to the bulls, which weigh in excess of 500 kilos (1,100 pounds).

The running of the bulls is monitored by experts who control the route and try to prevent accidents, but, inevitably, runners fall, suffer cuts and bruises, and are even gored by the animals.

Four people were gored at the 2012 San Fermin festival, while 41 were transported to hospitals and 388 others were treated at the scene by paramedics for a variety of injuries. EFE