On July 3rd 2006, a train derailed on Line 1 of Valencia's metro railway system. Forty-three people were killed and a further 43 people were injured.
The cause of the accident remains unknown but black box recordings from the train revealed it was travelling at twice the recommended speed of 40kph (25 miles) when it came off the tracks.
Initial judicial investigations in 2006 and 2007 laid the blame at the feet of the train's driver, who died in the accident.
But on Thursday judge Nieves Molina called in three technical directors of Valencia's public rail company, FGV, to face questioning. Those directors were responsible for overseeing the breaking system which failed to slow the derailed train, Spain's La Vanguardia newspaper reported.
The move marks a turning point in the case as it is the first time anyone from FGV has faced questions in court.
The case — and the victim's campaign for justice — made news again in April 2013 when high-profile Spanish journalist Jordi Evole dedicated a show to the incident.
During the show Evole embarrassed a senior official by approaching him unexpectedly in a market, questioning him about a victim's family that claimed to have been offered a job in return for not pressing charges.
Refusing to answer the questions, the official ended up cornered by onlookers shouting for him to respond.
The Valencia metro accident was one of Spain's worst rail accidents. In July 2013, 79 people died when a high-speed train came off the tracks near the pilgrimage city of Santiago de Compostela.