JK Rowling's Harry Potter spin-off Fantastic Beasts and Where to Find Them is to be a film trilogy, according to comments made by the head of Hollywood studio Warner Bros.

Kevin Tsujihara broke the news in a profile in the New York Times over the weekend, the newspaper describing the film as "three megamovies".

Fantastic Beasts, which is set 70 years prior to the arrival of Potter and his pals at the magical Hogwarts School of Witchcraft and Wizardry, will feature the swashbuckling adventurer Newt Scamander. The title is borrowed from the first-year textbook that Potter uses at Hogwarts school in the novel Harry Potter and the Philosopher's Stone.

Rowling published the Fantastic Beasts Magizoology compendium in 2001 to raise money for the charity Comic Relief. She will write her debut screenplay for the first movie in the series, a development she told the Times was entirely down to new Warner CEO Tsujihara's arrival at the studio.

"When I say he made Fantastic Beasts happen, it isn't PR-speak but the literal truth," Rowling told the newspaper. "We had one dinner, a follow-up telephone call, and then I got out the rough draft that I'd thought was going to be an interesting bit of memorabilia for my kids and started rewriting!"

Rowling added: "When Kevin got the top job, he brought a new energy, which rubbed off. He's a very engaging person, thoughtful and funny."

Fantastic Beasts, which was announced in September, does not yet have a director or start date, let alone a cast. Nevertheless, the new saga is firmly in the spotlight due to the huge box office success of the Harry Potter films. The series is the highest grossing film franchise in history, with $7.7bn (£4.6bn) in box office receipts.