Rescue crews are working to pull out people still believed to be trapped under the rubble, according to Juan Manuel Mendez, head of the emergency operations centre.
Mendez did not give a tally for the number of people believed to have been inside the Jet Set nightclub, near the coast of the Dominican capital, at the time of the incident.
Nelsy Cruz, the governor of Montecristi, was among the victims.
Meanwhile, the injured include merengue singer Rubby Pérez, who was performing when the roof collapsed, officials said.
His manager, Enrique Paulino, whose shirt was spattered with blood, told reporters at the scene that the concert began shortly before midnight, with the roof collapsing almost an hour later, killing the group's saxophonist.
"It happened so quickly. I managed to throw myself into a corner," he said, adding that he initially thought it was an earthquake.
President Luis Abinader wrote on X that all rescue agencies are "working tirelessly" to help those affected.
"We deeply regret the tragedy that occurred at the Jet Set nightclub. We have been following the incident minute by minute since it occurred," he wrote.
Abinader arrived at the scene and hugged those looking for friends and family, some with tears streaming down their faces.
He did not speak to reporters.
An official with a megaphone stood outside the club imploring the large crowd that had gathered to search for friends and relatives to give ambulances space.
"You have to co-operate with authorities, please," he said.
"We are removing people."
At one hospital where the injured were taken, an official stood outside reading aloud the names of survivors as a crowd gathered around her and yelled out the names of their loved ones.
It was not immediately clear what caused the roof to collapse.
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