LOS ANGELES — The Los Angeles County Sheriff’s Department announced Wednesday it plans to re-test about 4,000 DNA samples after learning the agency used testing kits over a roughly eight-month period that were found by the manufacturer to occasionally deliver incomplete results.

According to the department, officials at the Scientific Services Bureau learned only Monday about a notice that was sent to the agency last year by a DNA testing kit manufacturer stating that “a specific lot of kits were prone to intermittently poor performance with potential to cause incomplete results or profiles.”

The notice was sent to the department on Aug. 28, 2024, but it was directed to a person who was no longer with the department. The notice by the manufacturer recommended that the use of the affected kits be discontinued, but the department continued using them for about eight months, between July 2024 and February 2025.

It was unclear exactly how many criminal investigations may have been impacted by the use of the affected kits. The sheriff’s department contended in a statement, however, that “the use of the affected kits may have led to incomplete or suboptimal results, but is not likely to have falsely identified any individual.”

But to determine the possible extent of the issue, the department will re-test about 4,000 samples, although such re-testing may not be possible in some cases due to the limited sample sizes available.

“We take the integrity of our criminal investigations and the reliability of our forensic testing very seriously,” Sheriff Robert Luna said in a statement. “We are committed to thoroughly addressing this important issue, ensuring transparency, and taking immediate corrective action to protect the accuracy of ongoing and future cases. The Sheriff’s Department is working diligently to assess the impact and to prevent such situations from occurring again.”

Sheriff’s officials said the department has begun an internal investigation into the matter, and it will “re-examine existing protocols, identify potential gaps and implement corrective measures to prevent this from occurring again.”

The department noted that other law enforcement agencies may have also been affected, including the District Attorney’s Office.

“Upon learning of this issue concerning forensic testing on Monday, the District Attorney’s Office has immediately started working with the Sheriff’s Department to assess the scope of the situation in order to ensure that those involved in criminal justice process — defendants, defense counsel, victims, prosecutors, law enforcement, the courts and the public — are kept abreast of developments and in a position to make informed decisions on any actions that may need to take place,” District Attorney Nathan Hochman said in a statement. “We will follow the facts in whichever direction they take us on any individual case and make decisions that are in full accordance with the law on how to remedy any particular situation that requires such remediation. Ensuring the integrity of the criminal justice process to build and maintain trust in its outcomes is paramount as we go forward.”