(CNN) -- Irregularities in drug evidence processed by a New York Police Department forensics technician are being investigated, putting into question all cases the technician has worked on in her 24 years on the job, police say.
On April 30, Mariem Megalla was working on a case with a large sample of drugs: 84 pouches of cocaine, said her lawyer, Benjamin Lieberman. She was later told to stop what she was working on and to take the samples back to Evidence Control.
On Friday morning, Internal Affairs arrived at her home to tell her that she was suspended without pay.
Anthony Schepis, executive assistant for the Bronx district attorney's office, said the NYPD notified the five district attorney's offices in New York on Thursday that a problem was being investigated in a case Megalla had been working on -- the case with 84 pouches of cocaine.
Schepis said the NYPD was looking into the possibility that labels on the samples had been switched. A sample that came back negative for cocaine was labeled as positive, or vice versa.
Lieberman said his client "vehemently denies" wrongdoing.
The Bronx DA's office immediately began looking for any other open cases that had involved Megalla, Schepis said. It found one in which Megalla was supposed to testify the next day. The defense attorney and judge were notified, and the trial has been postponed.
The district attorneys' offices covering Brooklyn, Queens and Staten Island would not comment, because the investigation is ongoing. The Manhattan DA's office said, "The integrity of evidence is critical to the criminal justice system. The Manhattan District Attorney's Office is working closely with the NYPD and the other New York City prosecutors to determine the appropriate next steps."
Part of the procedure to identify samples is to take them to a molecular chemist for confirmation, Lieberman said. When Megalla arrives at work, she reports to Evidence Control to receive the sample she'll be working with that day. After she does some preliminary tests, she takes the samples to a molecular chemist for confirmation. Megalla then picks the samples up from the chemist, compiles a report and takes them back to Evidence Control at the end of the day.
Lieberman said it's possible that on the way to or from the molecular chemist, a label may have been switched.
As the NYPD investigates the cocaine case, the Bronx DA's office will be notifying defense attorneys from cases with which Megalla was involved, both open and closed, to see whether they want their cases to be re-evaluated. Schepis said several cases will "absolutely" be reopened.
"It's more work, but that's our job at the DA's office. We have to make sure that every defendant has a trial based on fair evidence that was tested properly and presented properly," he said.
Schepis said it is too soon to tell how many cases will become involved, because the investigation is still in its early stages. But he said the office will start by looking at the cases from the past year and work backward as far as necessary, even to October 1986, when Megalla began working as a lab tech.