Bolton's Alonso involved in fatal crash
The smash occured early on Monday morning and resulted in the death of a man in his early twenties and injuries to two passengers who were all travelling in Alonso's vehicle, a court spokesman said.
Alonso, 20, was released late on Monday and is also being investigated for causing reckless injury and infringing traffic regulations, the court statement said.
"Furthermore, the judge has moved to confiscate (Alonso's) driving licence and impose a driving ban covering the whole of Spain during the legal process," it added.
Alonso joined Bolton Wanderers from Real Madrid last summer and signed a three-year deal with the English Premier League club. His grandfather represented Real in the late-1950s and early 1960s, and his father had a five-year spell with Barcelona in the mid-1980s.
Alonso has made four appearances in the Premier League this season, according to the club's website.