Update: A gambling debt may have been involved in this mass killing, according to KTVU and its police sources. The investigation continues.
Five people -- three females and two males -- have been found dead in a home in San Francisco, according to police. It is being classified as a multiple homicide.
At least two of the victims were shot, but investigators were still looking into the cause of death for the others, according to police spokesman Cmdr. Lyn Tomioka.
Four of the five people found dead were related, police officials said. Investigators are still trying to determine what led to the multiple homicides, which were reported at 7:47 a.m. at 16 Howth St. in the city's Ingleside neighborhood.
A relative opened the door to the home with a key and discovered three bodies, one man dead just inside the door, and a man and woman on the garage floor. That relative called police who arrived and searched the home.
They found two more bodies: a woman at the rear of the home and one upstairs. All of them were adults.
"Obviously, this is a very tragic situation, no matter what happens and what we're able to determine," said SFPD Police Chief Greg Suhr.
The residence is at 16 Howth St. Howth Street is closed between Geneva Avenue and Niagra Avenue. The Ocean Avenue off-ramp from the 280 is unaffected.
"We believe at this time, this is specific to this residence," said Suhr. "We have information following up, but I want to assure the public that we don't believe we have anybody at large that's going to be doing random acts."
NBC Bay Area is sending a crew. Please check back for more details as they become available.
The Associated Press and Bay City News contributed to this report.