HAVANA, Cuba (AP) — Relatives of the missing in Cuba’s capital desperately searched Saturday for victims of an explosion at one of Havana’s most luxurious hotels that killed at least 26 people.

They checked the morgue, hospitals and if unsuccessful, they returned to the partially collapsed Hotel Saratoga, where rescuers used dogs to hunt for survivors.

A natural gas leak was the apparent cause of Friday’s blast at the 96-room hotel. The 19th-century structure in the Old Havana neighbourhood did not have any guests at the time because it was undergoing renovations ahead of a planned Tuesday reopening after being closed.

Havana city officials raised the death toll to 26 on Saturday, according to the official Cubadebate news site. The dead included four children and a pregnant woman.

Spain’s President Pedro Sánchez said via Twitter that a Spanish tourist was among the dead and that another Spaniard was seriously injured. Cuban authorities had not provided details on the tourist’s death.

Search and rescue teams worked through the night and into Saturday, using ladders to descend through the rubble and twisted metal into the hotel’s basement as heavy machinery gingerly moved away piles of the building’s façade to allow access.

Above, chunks of drywall dangled from wires, desks sat seemingly undisturbed inches from the void where the front of the building cleaved away.

Rescuers declined to answer questions because the authorities had ordered them to avoid confusion.

At least one survivor was found early Saturday in the shattered ruins, and rescuers using search dogs clambered over huge chunks of concrete looking for more.

READ: Death toll climbs to 22 in Havana hotel blast, gas leak suspected

Relatives of missing people remained at the site while others gathered at hospitals where the injured were being treated.