MADRID: The 13 students killed in a bus crash in northeastern Spain this weekend were all women from other countries, including seven from Italy, a Catalan regional government official said Monday.

The other six included two Germans, an Austrian, a French woman, a Romanian and an Uzbekistani, Interior department director Jordi Jane said.

Jane told reporters the victims were aged between 19 and 25 years.

The bus carrying 57 university students crashed Sunday near Freginals, halfway between the eastern coastal cities of Barcelona and Valencia. They were returning from a firework festival in Valencia.

The students were studying in Barcelona as part of the Erasmus exchange program. Barcelona University planned to hold five minutes of silence at noon in memory of the students.

Twenty-three of the passengers remained in hospital, including six in serious condition, Jane said.

The official said the bus driver was being investigated for possible negligent homicide. The driver was initially reported to have been uninjured but was taken into a hospital in the town of Tortosa late Sunday with lung problems.

He had been due to appear before a judge on Monday but the session was postponed.

Road conditions were good at the time of the crash. Spanish Interior Minister Jorge Fernandez Diaz said Sunday that the driver had passed alcohol and drug tests.

Jane said families of the victims were arriving in Catalonia on Monday.

The Erasmus program provides foreign exchange courses for students, mostly from the 28-nation European Union.