Mayor Enrique Maya heralded the first of nine days of uninterrupted festivities in the northern town as he lit the fuse from a balcony overlooking a frenzied crowd.
"Men and women of Pamplona, Long Live San Fermin!" Maya screamed, as revelers sprayed a fountain of wine, sangria, water and cava into the air. Many used toy water pistols, or leather wineskins to squirt alcohol into the mouths of those who asked. Onlookers on balconies followed suit.
"It's way more than we expected, especially just the energy. And this is only, what, the opening?" said 37-year-old Brooklyn native Malika Oyo, who was partaking with her brother Yaka.
"We need sangria, we need sangria right now," she said.
The day before the bulls steam through Pamplona's streets, its the turn of locals and foreigners -- nearly all dressed in white; red handkerchiefs tied around necks once the chupinazo has been fired.
"Everything happened so quickly... I screamed with all of my might, but the truth is from here (in the crowds) you can't hear a thing," Maya said.
As the sea of people sang along to "Ole, Ole, Ole," giant beach balls were punched to and fro."Seven Nation Army" by The White Stripes suddenly became another crowd favorite, many humming along, interspersed by the occasional fevered chant of "San Fermin" or "alcohol."
The Red Cross said it attended to 15 people with five taken to hospital for treatment to injuries.
"The ambiance is incredible, there's so much excitement in the air, there's a rush here you don't feel anywhere else," said 28-year-old Pamplona local Edurne Berastegi.
Immortalized in Ernest Hemingway's 1926 novel "The Sun Also Rises," the San Fermin festival is known around the world for the daily running of the bulls and all-night partying.
The first of eight dashes comes Thursday when thousands look to outrun six fearsome bulls along a narrow 875 yards (800 meters) course through the city's cobblestone streets, with both beast and human often falling over -- stomping on each other as they go.
"I'm planning on staying up ... partying until about 4 and then running tomorrow. I'm thinking about running this stretch here out of the square into 'dead man's' corner," said 28-year-old Australian tourist Dylan McLaren.
McLaren's white shirt had turned completely purple after being soaked in wine and other liquids. As was his girlfriend -- who didn't seem to be particularly enamored by the occasion: "She's not very happy about that, not happy at all," he added.
The 8 a.m. runs take place daily until July 14 with each charge broadcast on state television. And then, on the afternoon of each day, the same bulls face matadors in the ring.
"We do it because it's craziness, it's total insanity. You purposely put yourself at risk -- it's a huge adrenaline rush," said 55-year-old Florida native Hal Ringeisen who was in Pamplona with his wife Linda and neighbor John Parris, 52. Parris claims to have run the event over 70 times since 1989.
"On a drunken night he talked my husband into doing it and it's been downhill ever since," Linda revealed.
Since record-keeping began in 1924, 15 people have been killed in the running of the bulls -- the last victim 27-year-old Spanish runner Daniel Jimeno Romero in 2009.
Yaka Oyo said he was planning on running the second and third day while his sister Malika remained unsure.
"I keep asking if women run and people keep saying 'no' so I want to run," she said.
"It's not the bull that worries me," she added "I'm more worried about the men knocking me down, and then the bull."