NEW YORK (CBSNewYork) — Thirteen current and former Metro-North Railroad employees were indicted Monday, on allegations that they helped others cheat on licensing exams for conductor and engineer positions.

The railroad administers a test for prospective conductors and locomotive engineers, designed to evaluate knowledge of braking controls, signals, speed limits, emergency procedures, and knowledge of lines and stations. Engineers also must pass tests for recertification every three years, according to the Manhattan District Attorney’s office.

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Nine defendants – Melanie Bannister, 34; Bernice Bell, 46; Omar Carrillo, 28; Dennis Degenfelder, 36; Joseph Fowler, 31; Patrick Jones, 35; Sean MacAuley, 39; John Twardy, 34; and Donald Finnerty, 47 – are charged with emailing photos of three different tests and the answers to the questions to other conductor candidates, according to the DA’s office.

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Defendant Degenfelder was allegedly able to access the exam and record part of it with his cellphone while the instructor was out of the room, prosecutors alleged. He then emailed it to others taking the exam, prosecutors said.

Three prospective engineers – Danielle Bonge, 45; Tony Carbone, 56; and Coltyn Reindel, 25, are charged with distributing digital copies of three different tests to other engineer candidates who had not yet taken the exam, prosecutors said. A fourth engineer candidate – Raymond Fuentes, 41 – was charged with emailing photos of completed answer sheets to an engineer who had not taken a recertification test, prosecutors said.

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Because of the cheating, eight tests at Grand Central Terminal were wrongfully obtained and distributed between November 2011 and May 2014, prosecutors said. All tests have since been replaced by new versions, prosecutors said.