BOSTON (CBS) –  A chemist from the State Crime Laboratory in Amherst has been arrested.

READ MORE: "Time for the village to step up": Volunteers help ease nationwide baby formula shortage

WBZ NewsRadio 1030’s Kim Tunnicliffe reports

Attorney General Martha Coakley announced Sunday, Sonja Farak, 35, of Northampton, was arrested Saturday night and charged with allegedly tampering with drug evidence, possessing class A drugs and possessing class B drugs.

Coakley said the two drugs were heroin and cocaine.

“These drugs were tested, they were tested fairly,” Coakley said. “The certificates were not impeached in any way but we allege for personal use, the drugs were then taken and in her possession or used.”

Farak is scheduled to be arraigned Tuesday in Eastern Hampshire District Court.

READ MORE: Video: Likely tornado spotted in Charlestown, New Hampshire

Coakley said she does not believe Farak’s arrest jeopardizes the reliability of drug certificates or puts into question the fairness of trials for drug defendants.

The Amherst Drug Laboratory stores and analyzes alleged controlled substances seized by local and state police.

On Friday, members of the Amherst Laboratory contacted State Police to report a discrepancy in the controlled substance inventory held in evidence, according to Coakley’s office.

State Police say after an investigation they believe Farak removed a substance from a case that had previously tested positive for cocaine and replaced it with a counterfeit substance that no longer tested positive.

In August, allegations first surfaced that Annie Dookhan had mishandled evidence in the Jamaica Plain State Drug Laboratory.

As many as 60,000 drug samples may have been compromised, calling into question thousands of drug convictions.

MORE NEWS: Bail hearing postponed for Nathan Carman, charged in mom's death at sea

Dookhan was indicted earlier this month.