At least 18 people are dead after the roof of a Santo Domingo nightclub collapsed early Tuesday, according to Dominican Republic police.

It’s not clear what caused the roof of the Jet Set nightclub, a renowned club in the National District, to collapse.

The disaster unfolded during a performance by merengue singer Rubby Perez, local media reported.

There were 121 ambulance transfers to different hospitals, and search and rescue efforts are underway, Juan Manuel Mendez, the nation’s director of emergency management operations, said in an update on Instagram around 8 a.m. The number of those hospitalized may be higher as multiple people may be transferred by an ambulance at a time.

“We are still working, searching for people in the rubble. We presume that many of them are still alive, that’s why the authorities here with their teams will not stop until we find the last person in that rubble,” Mendez said in a video shared on the Dominican Republic National Police Instagram page.

Rubby Perez was found and is in stable condition, the singer’s manager, Evelio Herrera, said in an Instagram post.

“Let’s keep praying that more people continue to appear alive,” Herrera added.

Photos of the scene by local media show the building’s fallen roof in pieces, crumbling cement walls and piles of debris.

“Our city wakes up to a terrible tragedy that occurred at the Jet Set nightclub. My deepest sympathy goes out to the families still waiting for news of their loved ones,” Santo Domingo Mayor Carolina Mejía de Garrigó wrote on X on Tuesday morning.

She said that the city’s national disaster response committee is active.

Dominican Republic President Luis Abinader toured the collapse site Tuesday morning and said the main objective was to “save lives.”