The woman showed up at the emergency room of Harrison Medical Center on Thursday at about 8:15 a.m. and claimed she had a bomb in her car.
Police checked her vehicle and spotted a "suspicious device" inside, so authorities closed the emergency room entrance and called in the Washington State Patrol's bomb squad to investigate, said Lt. Pete Fisher of the Bremerton police.
The investigation confirmed she did have a "device," Poulsbo police said. So far, investigators won't say whether the device was some type of makeshift bomb or not.
As WSP bomb squad members removed the device, police rushed to her residence in Poulsbo, a mobile home park in the 1800 block of Lincoln Road, and evacuated homes in the area in case there were more devices there.
A few hours later, authorities executed a search warrant to look for any dangerous devices in her home.
The 43-year-old woman was arrested for unlawful possession of an explosive.