The forensic investigator tasked with determining whether a newfound set of human remains belonged to Natalee Holloway confirmed Thursday he’d made headway in the testing. Jason Kolowski, the former Forensic Laboratory Director of the D.C. Department of Forensic Sciences, said the DNA belonged to a single person.

“They are human,” Kolowski told Oxygen.com. “And they are of Caucasian, European descent.”

Natalee, who went missing in 2005, was Caucasian and of European descent. The 18-year-old was officially declared dead in 2012, but her body was never found. An investigation undertaken by Natalee’s father, Dave Holloway, and private investigator TJ Ward, uncovered the new human remains at an undisclosed location in Aruba.

Natalee Holloway (L) disappeared in 2005. Her body was never found.

“We are in the dark as to whether these remains are male or female, genetically,” Kolowski told Oxygen.

The gender would be confirmed sometime in September, Kolowski said. The testing was taking longer than is typical due to the nature of the DNA: the bone fragments contained mitochondrial DNA instead of the more commonly found nuclear DNA. When testing was completed, Kolowski said, he was confident he’d have a definitive answer as to whether they belonged to Natalee.

The Holloways took it upon themselves to continue searching for Natalee after they felt unsatisfied with the investigation by Aruban authorities. Her father, appearing in an episode of “Nightline” this week, said officials on the island “took their eyes off the last three people who were known to be with Natalee.” Dave Holloway was referring to the three men with whom Natalee was spotted getting into a car with on the last night she was ever seen. All the men were questioned but ultimately released for a lack of evidence. One of them, a Dutch man named Joran van der Sloot, remained the primary suspect in the case.

Aruban authorities officially closed the case in 2008.

“Little did they know, they weren’t just looking for a kidnapper or killer, they were up against the whole Aruban government,” Nancy Grace said on “Nightline” this week.

Natalee’s father called the newfound human remains “the most credible lead I’ve seen in the last 12 years.” The Holloways, however, are once again up against Aruban authorities. Aruban Public Prosecutor Dorean Kardol disputed the claim that human remains were found recently on the island.

“During an investigation by police in the area indicated by Mr. Holloway, we found remains,” Kardol told HuffPost last week. “But they were found to be from animals.”