A Sacramento couple is in jail Wednesday night on charges related to allegedly hiding an explosive device outside the downtown federal courthouse last weekend.

The FBI on Wednesday arrested Matthew Fraticelli, 30, and Stephanie Ann Shinn, 35, of South Sacramento on charges of attempted arson of a federal facility and possession of an unregistered destructive device.

Wednesday afternoon, the two had an initial appearance in federal court at the Robert T. Matsui Federal Courthouse at 501 I St. -- the same building where the device was found.

Fraticelli was convicted about two years ago in the state court system for possession of a destructive device, said the FBI’s Sacramento Division Special Agent in Charge Drew Parenti. The FBI has not yet uncovered a motive and has no reason to believe the couple is affiliated with a political organization.

The name “Fraticelli” was written in bold black letters on the explosive’s container, said FBI spokesperson Steve Dupre.

“We would describe that as a very useful clue in the investigation,” Parenti said.

The device was built with a five-liter aluminum Heineken keg filled with one gallon of flammable liquid and what appeared to be an M-80 pyrotechnic device with a fuse strapped to the keg with duct tape. The M-80 stuck out of a pill bottle containing a dark powder later found to work as a pyrotechnic material.

“That’s a high-powered firecracker,” Dupre said. “It’s not a little bitty firecracker you light on the Fourth of July. It’s a more powerful device.”

A federal protection service officer on a routine perimeter check discovered the device in front of the door of a small security kiosk on 6th Street just before 5 a.m. Sunday. The kiosk is a one-person booth outside a courthouse security gate. No one was in the kiosk when the bomb was left, Dupre said.

Surveillance cameras showed a couple fitting Fraticelli’s and Shinn’s descriptions near the courthouse, according to a sworn FBI affidavit. The woman was walking behind the man and pushing a stroller with a toddler inside northbound on 6th Street between I and H streets. The man was filmed carrying a brown paper shopping bag on 6th Street and then leaving video surveillance near the guard kiosk.

He soon reappeared on camera, running without the paper bag. He met up with the woman and baby stroller, and they jogged out of view. FBI agents can’t yet comment on why the device was apparently not set off.

Fraticelli and Shinn were arrested just after 7 a.m. after FBI agents tracked them to the house where they appear to live together with other adults and several children.

The FBI believes a 1-year-old child at the house was the one in the stroller. Wednesday afternoon, authorities did not yet know which adults were the parents of the children. Child Protective Services was called in after the couple was arrested.

Fraticelli is being held without bail. Shinn, who doesn’t appear to have a previous record involving explosive devices, has a detention hearing set for May 27, when a judge will determine whether she’s a flight risk or a danger to the community.

The arson charge carries a possible sentence of at least five but no more than 20 years. Possession of a destructive device carries a sentence of up to 10 years, Dupre said.

Fraticelli has a criminal record stretching back to 2000 that includes a report of a possible attack on Shinn on Valentine’s Day, 2009.

Sacramento Police and agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives aided in the investigation.

Sunday morning, Sacramento Police investigated another call about a suspicious item found on the street near Denny's at the northeast corner of 3rd and J streets. The item was a water bottle whose top was on fire, said Sacramento Police Sgt. Norm Leong.

On April 30, two “suspicious packages” were reported to have been left on a statue outside the Capitol. One was a paper bag containing clothes. Neither was found to be a bomb.