The San Francisco Police Department are investigating two separate deaths of women across the city, possibly taking SF to the second-highest number of homicides it has seen in the past five years.

Details remain scarce on both cases, and a call to SFPD was not returned at publication time. But here's what we do know, based on SFPD's general recap of "major" calls and information from the San Francisco Medical Examiner's office:

12:35 a.m. on Friday, December 18: The ME's office says that 58-year-old Maryanne Descalso was found on the 400 block of Ellis Street, which is between Leavenworth and Jones Streets. She was transported to San Francisco General Hospital, where she was pronounced dead, police say. The ME's office has yet to announce a cause of death, and SFPD has not provided any details on the circumstances of her passing, saying only that the weapon that caused her demise is "unknown."

No one has been arrested, nor have police released any suspect information, but they say that Descalso's death is being investigated as a homicide.

6:30 a.m. on Friday, December 18: The ME's office says that it was 33-year-old Allison Sparrow who was discovered unresponsive on the 2700 block of 16th Street, which is between Harrison and Folsom Streets. She was taken to SF General, where she was pronounced dead on arrival.

As with Descalso's case, police have yet to announce how Sparrow died, saying again that the case is being investigated as a homicide. As of Monday morning, no arrests have been made, and no suspects have been named in her death.

If SFPD (in conjunction with the ME's office) definitively determines that both Descalso's and Sparrow's deaths were foul play, they would be SF's 50th and 51st homicides for 2015, following the fatal beating of Stuart "Stu" Jackson earlier this month. San Francisco had 45 homicides for all of 2014, 48 in 2013, 68 in 2012, and 50 in 2011.

Related: Fatal Beating Of North Beach Artist Takes SF To 49 Homicides For 2015