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.