By DAILY MAIL REPORTER
Olé: An enormous crowd in Pamplona celebrate the start of the city's world-famous bull-running festival
The sangria was flying everywhere as revellers in the city of Pamplona celebrated the first day of the world-famous San Fermin bull-running festival.
Tens of thousands of locals and tourists packed into the main Plaza del Ayuntamiento as the traditional shout of 'Viva San Fermin', was broadcast from a city hall balcony.
At 12.00pm precisely a firework, known as the chupinazo was set off to officially mark the start as the writhing mass of people dressed in white waved the traditional red handkerchiefs.
Seeing red: Thousands of people wave red scarfs as they cram into Pamplona's city hall square after the firing of a firecracker known as the 'chupinazo', which is set off to announce the start of the festival
The crowd, dressed in traditional red and white, salute the firing of the Chupinazo firework which marks the beginning of the festival
The nine-day festival, made famous by Ernest Hemingway's 1926 novel The Sun Also Rises, is an alcohol and danger-fuelled event during which many people are seriously injured and sometimes killed.
Every morning of the festival a dozen or so animals are released from a holding pen and charge through the city streets on their way to the bull ring.
Each bull run takes around four minutes and involves between 2,000 and 3,500 people running alongside the animals while desperately trying to avoid being gored or trampled.
Every year between 200 and 300 people are injured. The vast majority are hurt after falling but some are trampled or gored by the bulls despite increased safety measures.
A band plays on as it slowly works its way through the hoards of revellers packing the city square
Wash-out: Ecstatic festival-goers are soaked with water thrown from a balcony. The first bull run will start at 8.00am tomorrow
Head over heels: A festival goer jumps from a fountain to be caught by the crowd during celebrations to mark the start of the festival
Two years ago a bull gored a 27-year-old Spanish man to death, piercing his neck, heart and lungs with its horns in front of the hordes of tourists.
In the evening, bulls killed in the ring are served up to hungry festival-goers in the city's restaurants.
This year organisers have launched a free iPhone app in English to help revellers to assess the chances that they will emerge from the festival unharmed.
It asks users about their behaviour at the festival, including how much they have had to drink and how many hours of sleep they have received.
Danger: A man is flipped over by a fighting bull during last year's celebrations. The first bull run of 2011 will take place at 8.00am on Thursday morning