OAKLAND — A 22-year-old woman attending the daylong hip hop music festival Hiero Day in downtown Oakland on Monday fell through a skylight atop a warehouse where dozens of concert goers had climbed to get a better view of some of the headline acts, according to an Oakland firefighter.

Around 5:20 p.m., when headlining rap artist Juvenile was scheduled to take the Full Circle Stage — one of three stages along 3rd Street between Filbert and Market streets — the unidentified woman fell about 20 to 25 feet through a warehouse skylight, Oakland Fire Battalion Chief Zoraida Diaz said. EMT cadets working the concert were the first on the scene at the warehouse at 3rd and Filbert, and she was taken by ambulance to the hospital. Her condition was unknown, Diaz said.

An attendee, who declined to give his name, said he saw dozens of people climb up a wall of a warehouse in that area, with the help of others, to get a better view of the stages. He said a crowd of people danced, shoulder-to-shoulder, at the edge of the building’s roof with almost no barrier and he was concerned someone would fall.

Photos and video on social media showed people lining rooftops listening to the music acts. In one video, one women is pushed up the side of the building to the roof, joining dozens of others.

Requests for comment to the festival promoter were not immediately returned. An Oakland police official had not heard of any falls at the concert.

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Contact Matthias Gafni at 925-952-5026. Follow him at Twitter.com/mgafni.