Madrid (AFP) - Rescue workers were scrambling Sunday to find survivors after a bus plunged into a river from a bridge in Galicia, northwest Spain, killing four people and leaving one or two missing.

At least four people were killed in the accident, which occurred Saturday just before 21:30 (20:30 GMT) on Christmas Eve in the town of Serdido-Cotopade, near Vigo, near the border with Portugal, according to local authorities.

The Galician emergency department announced in a tweet that it had recovered the bodies of two of the bus passengers from Saturday night to Sunday. She added that two other people, including the bus driver, were rescued and taken to hospital.

Rescuers found the other two bodies at noon Sunday, according to a Civil Guard spokesperson.

The spokesman indicated that one or two persons are still missing.

"The exact number is not known," he told AFP, as the driver was "not sure" how many people were on board the bus at the time of the accident.

According to the authorities, the four people who died were a young Peruvian woman who was working for an elderly person in Galicia, and three Spaniards living in the area.

An aerial view of the bus submerged in the raging river was published on social media.

A spokesman for the Civil Guard in Pontevedra, located on the Atlantic coast and far from the scene of the accident, explained

About 30 kilometers away, he told AFP that the accident occurred in a "very deep" place and therefore difficult to reach.

The spokesman noted that large equipment has been deployed to find the three missing passengers. The causes of the accident are still unknown. The bus driver - who provided information to rescuers about the number of passengers in the vehicle - tested negative for alcohol and drugs, according to the Guardia Civil.

The newspaper "La Voth de Galicia" reported that the bus was carrying a group of people on their way back from visiting relatives held in the Monterosso prison center in central Galicia.