Madrid (CNN) -- The judge in charge of the investigation into a horrific train crash in Spain last month has presented preliminary charges against the state-run rail infrastructure company, Adif.
Until now, attention has focused on the driver of the train, which derailed near the northwestern city of Santiago de Compostela, killing 79 people and injuring scores more.
Francisco Jose Garzon faces 79 counts of homicide by professional recklessness and an undetermined number of counts of causing injury by professional recklessness.
But preliminary charges have now also been filed by Judge Luis Alaez Legeren against "the person or persons from ADIF responsible for the traffic safety in the stretch of the rail line between the stations of Ourense and Santiago on July 24," according to documents posted on a court website Tuesday.
It's not yet clear who the individuals are.
The judge also requested more information on traffic safety and speed limits on that stretch of line from both Adif and state railroad company Renfe, and asked the Transport Ministry for details of any other incidents there.
A spokeswoman for Adif declined to comment on the charges Wednesday but told CNN the company would work with authorities as far as possible.
Garzon took control of the train at Ourense station, about 35 minutes before the crash occurred, a senior rail official told lawmakers during a rail safety briefing called after the disaster.
Lawmakers heard that the route the train was on, from Madrid to Ferrol, includes a mix of conventional and high-speed track, with the latter allowing high-speed trains to travel at over 200 kilometers per hour (124 mph.)
Two different safety systems are used in Spain: the European Rail Traffic Management System for the high-speed track and another known as ASFA on conventional lines.
The train and its engineer were switching between the two kinds of track and operating system in the course of the journey. One such transition occurred shortly before the crash.
Court officials have said the train was traveling at 153 kph (95 mph) when it derailed, nearly twice the speed limit on the curve where the accident happened.
The driver, Garzon, has been given conditional release while the investigation continues but has surrendered his passport.
CNN's Laura Perez Maestro reported from Madrid, and Laura Smith-Spark wrote in London.