Investigators are puzzled by the death of two pre-teen siblings whose skeletons were found in a California storage unit.

Investigators said Tuesday that dental records identified them as Victor and Tricia Reyes (RAY'-ess). They had been dead for two to four years when the discovery of a severed hand last month led detectives to search a Derrell's Mini Storage unit in Bakersfield.

But authorities don't know how they died.

A coroner says they appeared to be 10 or 11. Police say that their mother died this year of a drug overdose and that their father lives in Mexico.

Investigators say that the woman's other children were known to child welfare officials but that she hid the other two from authorities.