PARIS — A powerful explosion tore through a bakery in central Paris early on Saturday, killing at least four people, including two firefighters, and leaving smoke, flames and scattered debris in its wake, the authorities said.

Police and city officials said the blast, which occurred on Rue de Trévise, was believed to have been caused by a gas leak.

The Paris prosecutor’s office said that 47 people had been injured by the explosion, 10 of them critically. Emergency medical workers used helicopters to help evacuate some of the injured, picking them on the square in front of the Paris Opera house and taking them to hospitals.

Spain’s Foreign Ministry said that a Spanish woman had also been killed in the blast, and that a Spanish couple were being treated in the hospital. Christophe Castaner, the French interior minister, said two Paris firefighters were among the dead.