TEMPLE TERRACE — For seven years, friends of Sandra Prince have believed the Temple Terrace woman was murdered.

But after years of investigation, two digs at a South Tampa house and the naming of Prince's boyfriend as a "person of interest," police never found the 59-year-old woman's body. The investigation remained classified as a "missing person" case.

On Thursday, Temple Terrace police upgraded it to a homicide investigation.

And they're offering a $100,000 reward for any information that leads to an arrest and conviction.

The move comes after the city convened a cold case review panel in July, consisting of Temple Terrace and Tampa police, the Florida Department of Law Enforcement, the FBI and anthropologists from the University of South Florida.

The group reviewed evidence and is using new forensic technology to re-examine previous finds, said police Sgt. Michael Lowell, who leads the agency's criminal investigation unit.

"There are things that came out of that study," Lowell said, declining to elaborate because the case is still active.

The $100,000 reward comes from money Prince's mother, Dovey Hamby, left the Temple Terrace Police Department when she died in March 2007. She willed about $470,000 to the agency.

Before she died, while the case was still fresh, Hamby had offered an $80,000 reward herself. But for years, a body — and a culprit — eluded police.

Prince, the respected co-founder of a Tampa drug treatment program, vanished from her Temple Terrace home. Neighbors reported her missing Jan. 3, 2006.

Police found her blood in her trunk.

In 2007, detectives named Prince's boyfriend of five years, Earl C. Pippin III, a "person of interest" in the case. He was the sole beneficiary of her $3.6 million estate, and he had stopped talking to police.

That year, police dug twice under a South Tampa home that Pippin owned.

They thought Prince might be buried there. Pippin had started building at the Vasconia Street address in 2006.

Records showed that a city inspector approved a newly poured concrete slab at the house two days after Prince was reported missing.

Police found no remains.

Five years after her disappearance, police say, the law would allow Pippin to claim Prince's estate. But he would need to petition the court.

Pippin has not done that, Lowell said Thursday.

Several of Prince's friends attended the Police Department's news conference Thursday to show support for Prince.

Though the case is old, they hope that someone could finally be ready to talk.

"The best hopes for a good outcome faded long ago," said friend Patrick Carney. "And now, any finality or accountability would be welcomed by her friends and family.

"Sandra deserves that peace and this community deserves the opportunity to account for its own."

Times staff writer Laura C. Morel contributed to this report. Jessica Vander Velde can be reached at jvandervelde@tampabay.com or (813) 226-3433.