SAPULPA, Oklahoma - Just weeks shy of the 21st anniversary of the disappearances of three people, authorities have confirmed remains thought to be the victims were found in Pawnee County.

According to the Oklahoma State Bureau of Investigation, the case is no longer cold and is being treated as a triple-homicide.

As earlier reported by News On 6 sources, the remains were found on private property in Pawnee County last month. OSBI confirmed that information at a news conference on Thursday morning. Creek County authorities also have made one arrest in the case.

Grover Prewitt, 60, of Bristow, has been charged with accessory after the fact in first-degree murder for his role in concealing that the people had been murdered and their bodies dumped in a hole originally dug for a septic tank on family property where he lived.

Creek County District Attorney Max Cook filed the charge immediately following the news conference. Prewitt is being held at the Creek County Justice Center on a $500,000 bond.

Investigators also announced a $5,000 reward for information leading to other arrests and convictions. They believe multiple people were involved in the murders of Wendy Camp, her 6-year-old daughter Cynthia Britto, and her sister-in-law Lisa Kregear, who were last seen in 1992.

OSBI representatives said the agency received a tip and began digging on private property near Jennings on April 15. The next day, three sets of skeletal remains were uncovered in an 8-foot grave behind a residence in rural Pawnee County.

Pawnee County land records show the property where the graves were unearthed was owned by Prewitt in 1992, The Cleveland American reported last week.  According to an affidavit released on Thursday, Grover Prewitt sold 5 acres of the 40 acres to his mother, Ida Prewitt. It was on that 5 acres where the bodies were found, according to authorities.

Agents said clothing recovered from the grave match that of the three who went missing in May 1992. As we reported earlier, Camp's sister, Aisha Hashmi, of Grand Prairie, Texas, submitted a DNA sample to authorities on April 16.

On May 29, 1992, Camp, Britto and Kregear traveled to Shamrock to visit Wendy's son. Camp was in a bitter custody battle with her ex-in laws, according to reports.

OSBI says the then-toddler lived with his father Chad Noe in Shamrock. Beverly Noe, Chad's mother, drove the three from Oklahoma City to Shamrock for visitation with the boy.

After the visit, Beverly Noe, the sister of Grover Prewitt, claims she was on her way to take the three back to OKC, but dropped them off at a Walmart in Chandler following an argument in the car. The victims were never seen or heard from again.

Beverly Noe and family matriarch Ida Prewitt were both under suspicion as the case unraveled two decades ago, although they were never arrested.

Ida Prewitt, 82, died in 2011, after she and Beverly Noe served prison time for felony arson and conspiracy. In 2006, they were convicted of intentionally setting fire to their Bristow residence to collect more than $83,000 from an insurance company, Creek County court records show. The 82-year-old Ida was serving a suspended sentence at the time of her death. Beverly Noe is on probation until 2017, DOC records say.

A $5,000 reward for information about the murders has been offered by the OSBI. If you have information, please call the hotline at 800-522-8017.

Tess Maune will have more on News On 6 at 5 and 6 p.m.