Runners sprint in front of Torrestrella fighting bulls at the entrance to the bullring during the first running of the bulls of the San Fermin festival in Pamplona July 7, 2011. [Photo/Agencies]

PAMPLONA - Thousands of thrill-seekers have run with the bulls on a crowded fourth day at the San Fermin festival in Pamplona. Eight people were injured but no one was gored.

Several runners tripped, fell and were trampled as crowds raced alongside the massive bulls of the famous Miura breeding estate.

The Sunday run is usually the biggest of the eight that take place annually and is particularly favored by aficionados because it traditionally features Miuras, renowned as Spain's largest fighting bulls.

Navarra Hospital reported eight people were receiving treatment for minor injuries including arm and head trauma. Pamplona experts at state television TVE said around 3,500 people had run with the bulls on Sunday.