12:40 PM PT -- Venezuelan authorities believe Valbuena and Castillo may have been victims of robbers who throw rocks onto roads to cause cars to crash and then steal from people inside the vehicle.
Yaracuy governor Julio León Heredia announced 4 suspects have been arrested after they were found with the players' belongings.
MLB infielders Luis Valbuena and Jose Castillo were killed in a car crash in Venezuela on Thursday ... after a car they were riding in veered off the road.
According to local reports ... 33-year-old Valbuena and Castillo, 37, were leaving their Venezuelan league game with Cardenales de Lara in Yaracuy when their driver either hit or swerved to avoid a rock ... and drove off the road.
The man driving the car was the chauffeur of their teammate, Carlos Rivero -- who survived the crash.
Photos of the accident have surfaced ... showing the van totally damaged and flipped on its side.
⚾️ Que Desgracia. Así quedó la Camioneta en la que se Trasladaban Luis Valbuena y José Castillo, quienes como sabemos, Fallecieron. Moribundos, los delincuentes Igual los Robaron. Saquearon Todo. Hay más de 100 Efectivos Limpiando la Zona. Ojalá los Consigan. pic.twitter.com/A7DRLd8y20