MADRID (Reuters) -A bus carrying Inditex workers crashed on Tuesday and got stuck at the exit of a tunnel in an almost vertical position in Pineda de Mar in Spain's Barcelona province, injuring dozens of people, authorities said.

The bus, with 52 people on board, was travelling between Barcelona and Tordera in the northeast, where Inditex, owner of the Zara fashion brand, has a plant, Xavier Amor, mayor of Pineda de Mar, told national broadcaster TVE.

Three passengers with serious injuries were flown by helicopter to hospitals. and dozens more were treated nearby or transferred to health centres with less severe wounds.

The driver had to be freed from the bus.

There was no immediate information on what caused the accident, which is being investigated by regional police.

Inditex declined to comment and referred to emergency services.

Traffic authorities warned drivers to avoid the area as emergency services expect work to remove the bus to take several hours, as a heavy-duty crane would be needed to lower and stabilise the bus.

(Reporting by Emma Pinedo; additional reporting by Corina Pons; Editing by Arun Koyyur and Bernadette Baum)