Updated

Investigators found human remains in a basement under fresh concrete after a brother and sister told them they had killed their mother and grandparents, authorities said Wednesday.

Investigators worked into early Wednesday digging up concrete in the grandparents' small, wood-frame home on the city's east side, and a forensic anthropologist was brought in to help gather evidence.

Kenneth Allen Jr. (search), 29, and his sister, Kari Allen (search), 18, had been pulled over for speeding Tuesday in Missouri. In the car, officers discovered bloody clothes and bedding, as well as jewelry, cash, credit cards and the driver's licenses of two older people in Indiana, St. Charles County, Mo., Sheriff's Lt. Craig McGuire said.

Indianapolis police identified the grandparents as Leander Bradley, 92, and Betty Bradley, and the mother as Sharon Allen.

Kari Allen told authorities she and her brother had killed them, dismembered them and buried them in the basement floor in the grandparents' home, McGuire said. Kenneth Allen also later admitted involvement, he said.

They were charged with receiving stolen property, and murder charges were planned, authorities said.

Police Lt. Paul Ciesielski said authorities believe the three were killed early last month. The sister told authorities the mother and grandmother were killed at the mother's apartment in Noblesville, an Indianapolis suburb, then the bodies were brought to the grandparents' house, where the grandfather was killed, Ciesielski said.