The fire broke out late on Wednesday evening, with nearby residents seeing smoke rising from the lot.
It was still ablaze nearly twelve hours later, Hertfordshire County Council told CNN.
“Hertfordshire County Council’s Fire and Rescue Service were called to reports of a fire at Warner Bros Studios in Leavesden in Hertfordshire at 11.29 p.m. (6.29 p.m. ET) on Wednesday 10 July,” the council said in a statement.
“Eighteen fire engines and support vehicles are currently at the scene as crews continue to tackle the fire. Three jets and one aerial ladder platform are in use,” they said, adding that the set was not being used at the time and there are no injuries.
The studio, which occupies a sprawling complex in Leavesden, offers popular tours of the sets and sound stages used in the Harry Potter films. The tours are still running on Thursday, according to the studio’s website.
Movies including “The Dark Knight” and installments of the Spider-Man and Bourne franchises have also been produced at the base.
Mark Hancock, who lives near the studios, told CNN: “We first heard it about 12:15 or so this morning when a number of fire engines went past my house. Then more arrived over the next half an hour or so.”
“There was quite a strong smell of smoke in the air as well. As I watched the smoke appeared to get thicker, so much so that we could see the flashing lights of the fire engines reflecting off the thick smoke,” he added.
“It was still going strong at about 1 a.m. When I woke up this morning it was still smouldering and when I left for work this morning, there was still a strong smell and taste of smoke in the air.”
CNN has contacted Warner Bros. for comment.
Warner Bros. and CNN share a parent company, WarnerMedia.