A Petaluma resident’s discovery of a pair of explosives that appeared to be grenades prompted police to put the area around McNear Circle near Petaluma Boulevard South on lock down about 2:30 p.m. Saturday.

The explosive devices, which appeared to be old and deactivated, were found in the resident’s yard, police reported.

The Sonoma County Sheriff’s Office bomb squad removed the devices, which upon closer inspection looked to be harmless, police said.

“At one point in time, long, long ago, they were grenades, but it looks like they were filled with concrete,” said Lt. Brian Miller.

Authorities lifted the security lockdown within about an hour.

You can reach Staff Writer Nick Rahaim at 707-521-5203 or nick.rahaim@pressdemocrat.com. On Twitter @nrahaim.