BOSTON (AP) — Lawmakers plan to join in the growing investigation into the mishandling of drug evidence by a former chemist at a now-closed state crime laboratory, House Speaker Robert DeLeo said Tuesday.

DeLeo, in a statement, said two legislative committees have begun a formal inquiry into the matter, which is also the subject of a criminal probe by the state attorney general.

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“Due to the sheer scope of the systematic mishandling of evidence at William Hinton Laboratory, we may not know for some time the full impacts of this crisis,” said DeLeo, a Democrat.

The legislative probe will “begin the process of learning the full truth of what went wrong, how we should best deal with the fallout and how we can prevent the same from occurring again,” he added.

Democratic Gov. Deval Patrick ordered the Boston lab closed last month. Authorities have not provided specific details about what the chemist, Annie Dookhan, did. But they have said her actions could put in jeopardy past drug convictions and ongoing criminal prosecutions.

State Public Health Commissioner John Auerbach resigned Monday in the wake of the crisis. Two former managers at the lab have also departed within the past week, and a third supervisor was facing disciplinary proceedings, officials said.

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Auerbach, who planned to address the media on Wednesday, has said it was clear there was “insufficient quality monitoring, reporting and investigating” on the part of lab supervisors and managers.

The public health agency oversaw the lab until July 1, when it was transferred to the control of state police under a budget directive.

Dookhan, who resigned in March, has not commented.

DeLeo said the House Committee on Post Audit and Oversight Committee, chaired by Rep. David Linsky, D-Natick, and the Joint Committee on Public Safety and Homeland Security, chaired in the House by Rep. Harold Naughton, D-Clinton, would conduct the legislative inquiry. No dates were set for hearings, but the speaker said the panels would meet with representatives of the Patrick administration, prosecutors and court officials among others.

Patrick has said that a special unit would be created to deal with the thousands of drug cases that involved evidence handled by Dookhan, with an emphasis on identifying any prison inmates who may have been convicted on the basis of tainted evidence. The governor was expected to shortly name someone to head the unit.

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Copyright 2012 The Associated Press.