An Alamo Square resident discovered human bones in a planter box last month, San Francisco police confirmed Wednesday.
The bones were found in the 1300 block of McAllister Street on Nov. 23 by a resident who was gardening at the time of the grisly discovery.
"He wasn't sure what to make of these bones, but they did appear to be of human remains," San Francisco Police Officer Carlos Manfredi said.
Investigators with the medical examiner's office later determined that the bones were human remains, police said.
Cadaver dogs brought in from the Marin County Sheriff's Department later searched the garden, indicating that more human remains may be present, according to police.
A small area where the dogs alerted has been excavated, but no additional remains were located. The case remains under investigation.
"Time is of the essence when you talk about human remains. The big question is when did it happen?How long were these bones in there?" Manfredi said. "We're trying to find witnesses, people in the neighborhood who may have seen something."
Further details were not immediately available.
NBC Bay Area's Cheryl Hurd contributed to this report.