SEATTLE (AP) _ FBI crime lab errors led to dismissal of an explosives charge Tuesday in the conspiracy trial of seven people accused of plotting to kill federal agents.

The charge was dropped after an FBI lab technician, Robert Heckman, testified about the errors and was grilled on a still-secret draft report by the Justice Department that criticized his work on other cases.

Heckman acknowledged that some explosives evidence had been mislabeled on lab reports issued in December in the militia case, and said the reports were corrected last week.

Heckman was the last prosecution witness before the government rested its case. Six Washington State Militia and Freemen activists and a sympathizer are charged with plotting to kill, attempt to kill or otherwise attack federal agents. Some of them also face weapons charges.

The FBI's handling of evidence in the militia case came under scrutiny after the draft report into a whistle blower's accusations prompted transfer of three supervisors from the lab at FBI headquarters in Washington, D.C.

U.S. District Judge John C. Coughenour released the sealed report to the defense to question Heckman and another FBI agent, and defense attorney Tom Hillier used it to attack Heckman's credibility.

Referring to accusations against Heckman, ``the report has concluded that you made improper additions to lab reports,'' Hillier asked.

``That's what the current draft says, yes,'' Heckman replied.

In his testimony about the lab's handling of the militia evidence, Heckman said a detonator had been mistakenly listed with an apparent pipe bomb, other evidence had attributed to the wrong defendant and a second detonator was listed with the wrong apparatus.

Assistant U.S. attorney Susan B. Dorhmann later agreed to drop one count against defendant John Lloyd Kirk, who is identified as a Freemen member.

Robert M. Leen, attorney for defendant William Smith, said the militia and Freemen had been wrongly linked in the case, and that FBI agents had been misled by an informant.