< p>NORTHAMPTON, Mass. (AP) — The district attorney has requested a full audit of all drug evidence at the now-closed state crime lab in Amherst going back at least a year after a chemist was charged this week with stealing and tampering with evidence.

Northwestern District Attorney David Sullivan says drugs still missing from the lab or tampered with are likely to affect the disposition of several cases in Hampshire, Franklin and Hampden counties, and could affect some convictions.

Chemist Sonja Farak, of Northampton, pleaded not guilty earlier this week to two counts of tampering with evidence and cocaine and heroin possession charges in Eastern Hampshire District Court Tuesday. She was freed on $5,000 bail.

Sullivan tells the Daily Hampshire Gazette (http://bit.ly/VbPlxJ ) that the case is "a big black cloud" over the lab.

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Information from: Daily Hampshire Gazette (Northampton, Mass.), http://www.gazettenet.com