The mysterious derailment of an Amtrak passenger train in the middle of the Arizona desert in an act of sabotage remains unsolved 25 years later – but not forgotten by the Phoenix FBI.

The 25th anniversary passed on Friday with an announcement from Phoenix FBI that a reward of up to $310,000 is still being offered collectively by multiple entities in exchange for information leading to the arrest and conviction of the individuals who tampered with a section of train tracks, plunging Amtrak’s Sunset Limited down a ravine, 70 miles southwest of Phoenix.

The Oct. 9, 1995, derailment at 1:30 a.m. killed Amtrak sleeping-car attendant Mitchell Bates, 41, and injured 113 passengers, including 22 seriously.

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Amtrak's Sunset Limited train derailed in rural Arizona on October 9, 1995. The sabotage remains unsolved.

Amtrak's Sunset Limited train derailed in rural Arizona on October 9, 1995. The sabotage remains unsolved. (FBI)

“A hallmark of the FBI is that we don’t forget,” said Sean Kaul, special agent in charge of the FBI Phoenix Field Office. “There were children on board the train as young as 9 months old, an innocent man lost his life, and many others were injured.

He said for 25 years the victims of this crime, and their families and friends, have suffered.

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“We will continue to aggressively pursue this investigation, for as long as it takes," Kaul said. “We are determined to seek justice for the victims of this senseless crime.”

The FBI says investigators at the scene found a note claiming responsibility and expressing anti-government sentiment. But investigators have not yet found those responsible.

“This was just six months after the Oklahoma City bombing, it was fresh on everyone’s minds. People were on edge,” said Michael Lum a member of an FBI task force still working the case.

Reports at the time said the note mentioned federal raids on right-wing extremists at Waco, Texas, and Ruby Ridge, Idaho, and was signed ``Sons of Gestapo,″ raising fears anti-government extremists carried out the sabotage.

But if the group ever existed it has never been heard from again.

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The FBI has also investigated the possibility that an individual with a grudge against Amtrak was responsible.

The sabotage involved removing railroad steel spikes and rigging an electrical chord to override Amtrak's safety alert system.