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.

Ack! A military explosive was discovered near AT&T Park this morning by a construction crew. "The crew stumbled onto the unidentified ordnance on the 100 block of Terry Francois Street shortly before 10 a.m.," according to reports.

While no evacuations have been ordered -- stay strong, China Basin worker bees! -- Third Street between King and Channel are currently closed while the investigation and extraction continues.

No injures have been reported. We'll will update as soon as we know more (or as soon as we hear a loud boom.)

UPDATE: Third Street is back open.

[Chron]

According to CBS 5 (interrupting us right in the middle of The People's Court, no less!) "East Contra Costa County residents are being evacuated from an area near the unincorporated town of Knightsen because of a possible explosive device found inside of a residential motor home."

Motor homes and explosive devices? Who could've imagined!? Anyway, that's all the info posted so far. We'll update as soon as more info becomes available.

Update: Taken (again!) from CBS 5: "Sheriff's spokesman Jimmy Lee said the device was found about 1:30 p.m. on Broadway by a man who said the device looked like dynamite.The bomb squad from the Walnut Creek Police Department responded and residents within a 1-mile radius of Broadway were ordered to evacuate."

Emergency telephone alert calls were made to "220 residents" living in the area, and the evacuees were sent to Delta Vista Middle School.