At least 13 people were killed and several others were injured when a fire early Sunday ripped through adjoining nightclubs in Spain, authorities said.

Search-and-rescue crews are still looking for people unaccounted for in the blaze in the town of Murcia in southern Spain, officials said.

Diego Seral, a spokesperson for the Spanish National Police, told reporters that the bodies of those who died were recovered from the Fonda nightclub, one of three adjoining clubs, which sustained the majority of fire damage.

Video released by Murcia Fire Service showed firefighters working to control flames inside the nightclub. The footage also showed part of a roof collapsing.

Seral said the roof collapse was making it difficult for crews to find other victims and to pinpoint where the fire ignited.

Witnesses told reporters that several birthday celebrations were taking place when the blaze broke out.

"I think we left 30 seconds to 1 minute before the alarms went off and all the lights went out (and) the screams saying there was a fire," one survivor, who was not identified, said. "Five family members and two friends are missing."

As firefighters battled the blaze, survivors stood outside the nightclub hugging and consoling each other as they waited for information.

Maria Delores Albellan, a spokesperson for the adjacent Teatre nightclub, told news reporters that the fire originated in the La Fonda nightclub and quickly spread to the other two adjoining clubs.

Murcia Mayor Jose Ballesta told reporters the fire erupted around 6 a.m. Sunday and that seven bodies were found in the same area on the first floor of La Fonda nightclub.

Ballesta declared three days of mourning for those who had died. Flags were lowered to half-staff outside the Murcia City Hall.

"We are devastated," Ballesta said on Spanish TV channel 24h.