The FBI’s crime lab has reduced its backlog of forensic DNA cases by 87 percent over the course of two years, according to a report released Tuesday by the Justice Department’s inspector general.

In his 38-page report, Inspector General Michael E. Horowitz attributed the “significant” reduction to an increase in staffing and more automation.

The FBI lab in Quantico conducts DNA testing on biological evidence taken from crime scenes and items of evidence, including envelopes, clothing and drinking glasses. In an August 2010 audit report, the Justice Department watchdog said the lab had a large backlog of cases in both its nuclear DNA unit, which mostly analyzes biological fluids, such as blood and semen, and in its mitochondrial DNA unit, which examines evidence, such as naturally shed hairs, hair fragments, bones and teeth.

In his report, Horowitz found that the nuclear unit had effectively eliminated its backlog, reducing the number of its cases from 2,722 in March 2010 to 110 as of March 2012. The remaining cases are a “monthly work-in-progress,” the report concluded.

But the mitochondrial DNA unit continues to have a backlog, Horowitz said. The unit reduced the number of its cases from 489 in March 2010 to 293 as of March 2012, but Horowitz said the reduction could not be attributed to the number of completed cases. Rather, he said, it was mostly due to a change in the way the unit calculates its backlog and other policy changes.

The new report also noted that the FBI lab is working with the FBI Office of General Counsel, the Justice Department and the Innocence Project, a New York-based advocacy group for people seeking exoneration through DNA testing, to prepare a plan for the review of historical mitochondrial DNA cases involving microscopic hair examinations.

“The plan is not yet finalized, but should DNA examinations be requested and certain conditions are met, the FBI has stated that it is available to provide mitochondrial DNA testing on the relevant hair evidence,” the report said.

In July, the Justice Department and the FBI launched a review of thousands of criminal cases to determine whether any defendants were wrongly convicted or deserve a new trial because of flawed forensic evidence.

The undertaking, the largest post-conviction review ever done by the FBI, comes after The Washington Post reported in April that Justice Department officials had known for years that flawed forensic work might have led to the convictions of potentially innocent people but had not performed a thorough review of the cases. In addition, prosecutors did not notify defendants or their attorneys even in many cases they knew were troubled.

The inspector general’s report said that the FBI lab still lacks a system capable of electronically managing laboratory operations, despite having spent at least $14 million since 2003 in two unsuccessful attempts to develop such a system. The lab is in the beginning stages of developing a new system, the report said.