The San Francisco Police Department was faced with a potentially explosive situation Thursday, when the manager of an apartment building discovered a grenade a former tenant had left behind.

Police say that they were called to the residence on the 800 block of Hayes Street, which is between Webster and Fillmore Streets on the westernmost edge of Hayes Valley, as 12:43 Thursday afternoon.

When they arrived, they were told that the residence in question had been vacant since August 15, when the last tenant, a 91-year-old man, had moved out. On Wednesday, the 61-year-old building manager for the apartment was cleaning the home, and discovered a hand grenade — with the pin still intact.

Police say that the building manager moved the blue-painted grenade into the building's back yard, and called police regarding the explosive device on the following day. The SFPD's Explosive Ordinance Disposal unit responded to the scene and "safely removed [the] device," according to the SFPD.