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

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From left: Shani Asa, Shullu Gorado and Luwiza Daman were arrested after what police described as a fake bomb was found in a carry-on bag during security screening on Friday at Phoenix Sky Harbor International Airport, police said Wednesday. ((Maricopa County Sheriff/Associated Press))

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 the upcoming 10th anniversary of the Sept. 11, 2001, terror attacks raised police concern in relation to the incident.

The refugees , who were arrested Friday, were being held in Marcicopa 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 could be filed as the investigation develops.

'One doesn't tape a cellphone to a container when you're going through airport security when you've got an ounce of sense.'— David Cid, counterterrorism expert

The refugees are Luwiza Daman, 51, from Ethiopia who was living in Des Moines, Iowa; Shullu Gorado, 25, and Shani Asa, 34, both of Eritrea, a small country on the Red Sea that borders Ethiopia in the Horn of Africa.

Gorado and Asa were living at separate 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, Dawit Abera, 36, 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 helps other refugees in the community,

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

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

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

He described the item as an organic substance inside a container, with a cellphone taped to the outside of the container. He said the organic, paste-like substance could be some type of food but said that it hadn't been identified. He was unable to describe the container.

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

Cellphone attached to container

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.

Martos said that Asa admitted to attaching the cellphone 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.

Because the item had a cellphone 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.

Cellphones 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 cellphone to a container when you're going through airport security when you've got an ounce of sense."