BROCKTON, Mass. – A former Massachusetts chemist accused of faking test results at a state drug lab pleaded not guilty Wednesday to six counts of obstruction of justice in a scandal that could jeopardize thousands of drug cases.

Annie Dookhan was indicted last month on a total of 27 charges accusing her of fabricating test results and tampering with drug evidence while testing substances in criminal cases.

Dookhan, 35, of Franklin, was arraigned Wednesday morning on five obstruction counts in Brockton Superior Court. She was arraigned later Wednesday on one obstruction count in Fall River Superior Court.

An estimated 200 convicted defendants have been released from jail and had their cases put on hold while their legal challenges are pending.

Authorities shut down the lab in August after Dookhan, while being questioned by state police, allegedly said she sometimes would take 15 to 25 samples, test only five of them, but then list them all as positive. She also allegedly acknowledged that if a sample tested negative, she would sometimes take known cocaine from another sample and add it to the negative sample to make it test positive.

Neither Dookhan nor her attorney, Nicolas Gordon, commented following the two arraignments.

She is accused in both counties of obstructing justice by falsely claiming she held a master’s degree in chemistry while testifying as an expert witness.

Plymouth District Attorney Timothy Cruz said prosecutors are reviewing every case handled by Dookhan to “make sure justice is done.”

But he said it is frustrating when convicted drug dealers are released back on the street because of Dookan’s alleged misconduct.

“People have been let out and some individuals have re-offended,” Cruz said.

“It’s frustrating not just for prosecutors, but for hard-working police officers. … Drug dealers, by nature, deal in the world of violence, so when these individuals are released back into the community, it poses difficult challenges for the police officers on the street.”

Dookhan resigned in March during an internal investigation by the state Department of Public Health.

State police closed the lab last summer after taking over its operation and discovering the extent of Dookhan’s alleged misconduct.

Dookhan has pleaded not guilty in five counties to charges that include obstruction, evidence tampering and perjury.

She faces one additional arraignment next week in Essex County.

The only potential motive offered by authorities so far is that Dookhan wanted to be seen as a good worker.

She remains free on $10,000 bail.