The arrest of three African refugees after a fake bomb was found in one of their carry-on bags at Phoenix's airport has authorities investigating whether the group was testing airport security.

Police haven't ruled out the possibility of terrorism but say they still don't know the motive behind the fake bomb. In a court document released to The Associated Press on Wednesday, one of the arresting officers wrote, "The suspicious package suggests subjects were testing airport security protocol."

Phoenix police Sgt. Steve Martos said Wednesday that the upcoming 10th anniversary of the 9/11 terror attacks raised police concern in relation to the incident.

The refugees were being held in Maricopa County jail on bonds of $75,000. They face felony charges of having a hoax device and conspiracy to obtain a hoax device, and police say more charges could be filed as the investigation develops.

The refugees are: Luwiza Daman, a 51-year-old woman from Ethiopia who was living in Des Moines, Iowa; Shullu Gorado, a 25-year-old man from Eritrea; and Shani Asa, a 34-year-old also of Eritrea, a small country on the Red Sea that borders Ethiopia in the Horn of Africa. Both Gorado and Asa were living at different apartments in Phoenix, and it's unclear when they all arrived in the U.S.

Daman, Gorado and Asa all declined to speak to The Associated Press on Wednesday through a sheriff's spokesman, and it's unclear whether any of them yet have lawyers.

Gorado's roommate, 36-year-old Dawit Abera, told the AP outside their apartment that Gorado works full-time for a cement company. He said his roommate of five months is honest, hardworking, sends money to his mother and brother back home and makes time to help other refugees in the community,

"He's too much of a good guy," Abera said. "I don't believe this news."

Martos said Daman was carrying a suspicious item in her carry-on bag Friday as she tried to get through security at Phoenix Sky Harbor International Airport and board a plane to Des Moines.

Transportation Security Administration workers alerted police, and that soon after that a bomb squad and hazardous materials crew arrived and found the item wasn't explosive, Martos said.

He described the item as an organic substance inside a container, with a cell phone taped to the outside. He said the paste-like substance had not been identified. He was unable to describe the container.

"Why would anybody want to take that onboard an airplane?" Martos. "We want to ensure people that we're going to look at this matter that we're taking it seriously."

Martos said that Daman told investigators that Gorado, an acquaintance, gave her the item to be delivered to someone in Des Moines. Police tracked down Gorado, who told them that he got the item from Asa.

Abera, who also is from Eritrea, said his roommate told a mutual friend who visited him in jail that Gorado had only brought food for Daman to take to Iowa.

Martos said that Asa admitted to attaching the cell phone to the container, and that he had been asked to have the item delivered to Des Moines.

Police have not identified the Des Moines contact who was supposed to receive the item.

TSA spokesman Greg Soule declined to discuss the incident, saying that it was in the hands of Phoenix police.

FBI spokesman Manuel Johnson said his agency was assisting Phoenix police in their investigation and referred all questions to them.

Because the item had a cell phone attached to it, police had to react with "an abundance of caution," said David Cid, the executive director of the Oklahoma City-based Memorial Institute for the Prevention of Terrorism who worked in counterterrorism at the FBI for 20 years.

Cell phones can be used to detonate bombs, either with alarms in the phone or with a phone call from another cell.

"It certainly raises red flags," Cid said. "One doesn't tape a cell phone to a container when you're going through airport security when you've got an ounce of sense.

"Is it possible that someone did this without thinking?" Cid said. "Yes, it's possible."

He said whatever the motive was behind the incident, "the system worked" and that authorities need to be especially cautious these days.

"Al-Qaida and its affiliates remain fascinated with attacking our air transportation system and they also are very fixated on mass casualties," Cid said. "And that's why air transportation continues to be targeted despite the fact that it's one of the targets that we have hardened more than any other."

Little is known about the suspects so far.

Gorado was charged in 2008 in Phoenix with reckless driving and endangerment. He accepted a plea deal to get the reckless driving charge dismissed and was sentenced to probation for endangerment.

Gorado's Facebook page shows pictures of him visiting the Las Vegas Strip, in front of a car with a bumper sticker showing a curvy woman and an American flag, and hanging out with friends.

John Wilken, bureau chief of the Iowa Board of Refugee Services, said that Daman recently moved to Des Moines and came to his office in July looking for help finding a job. He didn't know anything else about her.


Associated Press Writer Terry Tang contributed to this report from Phoenix, and AP Writer Luke Meredith contributed from Des Moines.

Follow Amanda Lee Myers on Twitter at http://twitter.com/#!/AmandaLeeAP

Phoenix police: http://phoenix.gov/POLICE/

Memorial Institute for the Prevention of Terrorism: http://www.mipt.org/Home.aspx