PHILADELPHIA — Prosecutors are appealing a judge’s decision to throw out criminal charges against the engineer in a deadly Amtrak derailment in Philadelphia.

The Pennsylvania attorney general’s office filed notice of its appeal on Tuesday in the only criminal case resulting from the May 2015 wreck.

Eight people died when the New York-bound train rounded a curve at more than twice the 50 mph speed limit and flew off the tracks.

Philadelphia’s district attorney declined to pursue a case against 34-year-old engineer Brandon Bostian. That led a victim’s family to seek charges on its own and state prosecutors to take over.

A judge dismissed the case last month, ruling that the evidence pointed to an accident. Federal safety investigators concluded Bostian lost track of where his train was.

Bostian’s lawyer didn’t immediately return a telephone message.