The District medical examiner’s office was awarded full accreditation by the national oversight board, making it the first time the medical examiner in the nation’s capital has ever received such a national ranking, the office said Wednesday.

In February, the National Association of Medical Examiners inspected the D.C. Office of the Chief Medical Examiner, and a month later it concluded that the office met its standards for full certification. The review followed a two-year overhaul of the office by the recently appointed chief medical examiner, Roger Mitchell.

Prior to 2011, the national board had certified the office only as partially accredited. But in 2011, the board withdrew the partial accreditation over concerns that the chief medical examiner at the time, Marie-Lydie Y. Pierre-Louis, was not board certified in pathology, as the association requires of top agency officials.

In 2014, then-Mayor Vincent C. Gray (D) replaced Pierre-Louis as chief medical examiner by hiring Mitchell. Mitchell, who is board certified, was the former assistant state medical examiner in New Jersey.

Mitchell put together a team of coroners that includes a former chief coroner from Columbus, Ohio. For the first time in recent history, all six of the office’s forensic pathologists are board certified.

Of the 300 medical examiner offices in the nation, only 73 are fully accredited, according to the office.

Prior to obtaining accreditation, the office said only about 38 percent of autopsy reports were completed within 90 days, which is below the standard created by the board. During the past year, according to the office, about 90 percent of autopsy reports are completed within that time period.

Delays in the completion of autopsy reports often resulted in delays in investigations, court cases and insurance payments to beneficiaries. And during murder trials in D.C. Superior Court, defense attorneys would often highlight that the office was not accredited in an effort to raise doubts concerning the medical examiner’s testimony.

The office is up for review for reaccreditation in five years.