LONDON — Keith Flint, a high-octane founding member of the British dance act the Prodigy, who sang lead vocals on the hits “Firestarter” and “Breathe,” was found dead on Monday in Essex, England. He was 49.

His death was announced on the band’s Instagram account. In a post on Monday, Liam Howlett, the band’s main musician, said Flint had killed himself.

“I can’t believe I’m saying this but our brother Keith took his own life over the weekend,” Mr. Howlett wrote, adding that he was angry, confused and heartbroken by the news.

The Prodigy was scheduled to tour the United States in May, with one show set for Terminal 5 in Manhattan. It has not been announced whether the shows will go ahead.

The Prodigy came to prominence in 1997 with “The Fat of the Land,” the group’s third studio album, which went to No. 1 in Britain and the United States and made underground British dance music a hit across the Atlantic.

Mr. Flint, with his distinctive double mohawk and endless energy, was one of the main factors behind the band’s appeal, along with the band’s other singer, Maxim Reality (Keith Palmer).

Mr. Flint and Maxim Reality were “folk devils” and “emissaries from techno’s psychic underworld,” Ann Powers, a New York Times pop music critic, wrote in 1998 in a review of the band’s live show.

Mr. Flint explained his look and onstage antics in a 2009 interview with The Guardian. After wearing his hair in a mohawk at school, he was “chucked out and sent to a special school,” he said. “They had to hypnotize me to settle me down — I just had so much energy.”

Being onstage was a release for him, he added. “It gets my mental energy out,” he said. “That’s why I’m really honest onstage. I’m not there for the beauty of my voice or to be the best dancer. I go out to express myself and stir up the audience.”Keith Charles Flint was born on Sept. 17, 1969, in Redbridge, in East London, and grew up in Braintree, a suburb in Essex. He had an unhappy childhood, and his parents split up when he was young. He told The Times of London that he stopped talking to his father entirely in later life.

Mr. Flint was bright but had dyslexia. That led to problems at school, and he left at age 15. He then went to work as a roofer, according to the BBC.

In 1989, Mr. Flint met Mr. Howlett at a rave and asked the D.J. for a mixtape. Mr. Howlett gave him one featuring some of his own tracks, writing the word “Prodigy” (the name of a synthesizer made by Moog) on the cover. Mr. Flint loved the music and suggested that he and a friend, Leeroy Thornhill, dance onstage as Mr. Howlett played.

The band found immediate success in Britain with its debut single, “Charly,” a dance track from 1991 based on a sample from a 1970s public information film about child safety: “Charley says always tell your mummy before you go off somewhere.” Mr. Flint, who had long hair at the time, danced manically throughout the song’s video.

The band’s popularity grew as the British government tried to clamp down on the country’s rave scene. The Prodigy’s second album, “Music for the Jilted Generation,” with its frenetic beats and defiant lyrics, caught the mood of rebellion as young people continued to stage outdoor parties despite a 1994 law banning them.

But the band’s popularity peaked only after Mr. Flint started singing. “Firestarter,” the first single from the Prodigy’s third album, “The Fat of the Land,” marked a change in direction, mixing rave music with rock guitars. “I’m a firestarter, twisted firestarter,” Mr. Flint sneered, playing the role of cartoon villain. “I’m the trouble starter, punking instigator.”

Mr. Flint sang on many other Prodigy releases (the band’s seventh album, “No Tourists,” was released last year), although none found as much success as “Firestarter” and “Breathe.”

“Baby’s Got a Temper,” a 2002 single, featured Mr. Flint singing in praise of Rohypnol, a drug associated with date rape. It was widely criticized and caused Mr. Howlett to rethink the band’s direction. Mr. Flint was dropped from singing on the band’s next album in favor of guest singers, although he continued to perform at live concerts and returned for “Invaders Must Die” in 2009.

Mr. Flint’s life sometimes involved problems with depression and prescription drugs. In 2009, he told The Times of London that he had once been suicidal.

His high-energy onstage antics were reflected in other interests, too. Mr. Flint was a lover of motorbikes and owned a successful motorcycle racing team. He also ran a pub in Essex for several years. In 2015, he told The Guardian that the bar had an open fireplace, and that every time he went to light it, somebody would make a “Firestarter” joke.

“I’m like, ‘That’s very funny, you owe me a pound,’ ” he recalled saying. He gave all the money collected to charity, he said.

Mr. Flint’s death prompted many tributes online, including from dance music stars and fans of the band.

“He did what all music stars are meant to do,” Kathy Burke, a British comedian and actress, wrote on Twitter. “He frightened your mums and dads.”