SACRAMENTO  (AP) — California officials offered a $50,000 reward Friday that they hope will finally help solve the slaying of a young family nearly 30 years ago and end the mystery surrounding an empty safe that may have held cash or gold.

State Department of Justice analyst Marcy Jacobs, 31, was fatally shot and stabbed in the family’s home in 1991. Her husband, Michael Jacobs, 33, was shot dead in the garage near an open and empty safe. Their 9-year-old daughter, Jennifer, was fatally shot in a bedroom.

Michael Jacobs was keeping the safe for a longtime friend, Richard “Ricky” McCarthy, who disappeared a few months earlier after being released from the Yolo County jail and is believed to be dead, Sacramento Police Detective Patrick Higgins said.

The safe may have contained “a large sum of money and perhaps gold,” he said. “We believe the killers went there for that purpose and nothing to do with the Jacobs family.”

DNA was recovered at the scene, and investigators believe at least two people were involved, Higgins said. They know people of interest but don’t have enough evidence to make an arrest, he said.

“Over the years, this case has been very challenging for multiple investigators,” Sacramento Police Chief Daniel Hahn said.

Sacramento police detectives working with the state justice department began actively investigating the case again because of recent advances in analyzing evidence collected long ago and the hope that someone will now come forward, Hahn said.

Officials said there is no known connection with Marcy Jacobs’ state job, but state Attorney General Xavier Becerra said the agency he runs “won’t rest until we’re able to bring justice to a former friend and colleague.”

A fellow department employee found the bodies when Jacobs didn’t show up for work. She was taking night classes to become a crime scene investigator.

Her husband was a contractor and carpenter for Fargo Construction in Sacramento. Their daughter, known as Jenny, was in the fourth grade.