A few weeks ago while walking his dog Ivy, a man from southwest Portland picked up a stray tennis ball. Although the ball looked a bit odd--it was wrapped in tape--he tossed it to his dog. A few minutes later, while in Ivy's mouth, the ball exploded, killing the dog.

What was odd about this incident is what the police said. "You'd be surprised how many calls we get like this," Officer Henry Groepper said. Yes, I would! Part of the reason I moved to Portland--instead of, say, Beirut--was precisely because of the lack of explosive devices lying around the streets and parkways.

Only two months ago, a 59-year-old man in Portland kicked a brown paper bag lying in his driveway. The bag exploded, blowing off his foot.

Alarmed by these two bombings, I began digging around to find out how volatile Portland actually is. It turns out it's much worse than I ever could have guessed. On the very same Sunday that a bomb exploded in a dog's mouth, another tennis ball bomb was discovered nearby. Moreover, within the past year, the Portland Explosive Disposal Unit has been alerted to about a half-dozen other such devices. In fact, the four full-time members of Portland's bomb squad are called out more than 500 times annually! While I was in high school, a few rabble rousers phoned in bomb threat to evacuate the school before exams. Maybe these 500 calls were just self-serving hoaxes.

No such luck, as it turns out. Sgt. Mike Unsworth, the lead tactician for Portland's Explosive Disposal Unit, told me, "We see a lot of pipe bombs." It also turns out there's a bevy of dynamite and mines lying around basements in town. It seems some vets brought home mines as souvenirs from Vietnam, stuffed them in their basements and forgot about them after moving out.

I pressed for more information, but Sgt. Unsworth would have none of it. "We try to keep it quiet," he said. But, he did say they host training courses for groundskeepers and park services rangers. Does that mean that there are bombs lying around Forest Park? Again, Sgt. Unsworth wouldn't say.

Although reward money has poured in since Ivy the dog was bombed, the police have no leads.