The Los Angeles County Sheriff’s Department says it will retest 4,000 DNA samples and open an internal investigation after learning that it used potentially flawed test kits for eight months.

The department recently learned that some kits “were prone to intermittently poor performance with potential to cause incomplete results or profiles.”

The Los Angeles County Sheriff's Department will retest more than 4,000 DNA samples after announcing it used a faulty testing kit for at least eight months.