HAVANA (AP) — A powerful explosion apparently caused by a natural gas leak killed at least 18 people, including a pregnant woman and a child, and injured dozens Friday when it blew away outer walls from a luxury hotel in the heart of Cuba’s capital.

No tourists were staying at Havana’s 96-room Hotel Saratoga because it was undergoing renovations, Havana Gov. Reinaldo García Zapata told the Communist Party newspaper Granma.

A sign for the five-star Hotel Saratoga hangs amid the rubble after it was heavily damaged by a deadly explosion in Old Havana, Cuba, Friday, May 6, 2022. (AP Photo/Ramon Espinosa)

“It’s not a bomb or an attack. It is a tragic accident,” President Miguel Díaz-Canel, who visited the site, said in a tweet.

Díaz-Canel told reporters that 50 adults and 14 children were hospitalized after the blast, and that families in buildings near the hotel affected by the explosion had been transferred to safer locations.

Cuban state TV reported that the blast was caused by a truck that had been supplying natural gas to the hotel, but did not provide details on how the gas ignited.

The blast sent smoke billowing into the air around the hotel with people on the street staring in awe, one saying “Oh my God,” and cars honking their horns as they sped away from the scene, video showed. It happened as Cuba is struggling to revive its key tourism sector that was devastated by the coronavirus pandemic.

Cuba’s national health minister, José Ángel Portal, told The Associated Press the number of injured could rise as the search continues for people who may be trapped in the rubble of the 19th century structure in the Old Havana neighborhood of the city.

“We are still looking for a large group of people who may be under the rubble,” Lt. Col. Noel Silva of the Fire Department said.

An elementary school next to the hotel was evacuated. It was not immediately clear if the injured children were students.

Police cordoned off the area as firefighters and rescue workers toiled inside the wreckage of the emblematic hotel about 110 yards (100 meters) from Cuba’s Capitol building.

The hotel was first renovated in 2005 as part of the Cuban government’s revival of Old Havana and is owned by the Cuban military’s tourism business arm, Grupo de Turismo Gaviota SA. The company said it was investigating the cause of the blast and did not immediately respond to an email seeking more details about the hotel and the renovation it was undergoing.