PHOENIX -- Three African refugees were arrested after what police described as a fake bomb was found in one of their carry-on bags during security screening at Phoenix Sky Harbor International Airport, police said Tuesday.

Phoenix police didn't yet know what the motive was behind the Friday incident and weren't ruling out the possibility of a terrorism connection, Phoenix police Sgt. Steve Martos said Tuesday.

Martos said that Luwiza Daman, a 51-year-old woman from Ethiopia, had the suspicious item in her carry-on bag as she tried to get through security at the airport Friday, and that Transportation Security Administration workers alerted police.

A bomb squad and a hazardous materials crew found that the item was not explosive, and Martos said it could not have hurt anyone.

He said that Daman told investigators that an acquaintance gave her the item to be delivered to someone in Des Moines.

Police tracked down the acquaintance, identified as 25-year-old Shullu Gorado of Eritrea, which is next to Ethiopia. Gorado told police that he got the item from another man, 34-year-old Shani Asa, also of Eritrea, Martos said.

Daman, Gorado and Asa all have been booked into Maricopa County jail on a charge of having a hoax device and conspiracy to obtain a hoax device. More charges may be filed as the investigation continues.

Martos did not know how long Daman, Gorado and Asa have been living in the U.S. He said Gorado and Asa most recently were living in Phoenix but did not know where Daman was living.

Martos described the incident as the first of its kind at Sky Harbor.