CARO, Mich.—The FBI said yesterday that it had no information to indicate that the three Texas men arrested with about 1,000 cell phones in their van had any direct connection to known terrorist groups.

Authorities had increased patrols on Michigan’s 5-mile-long Mackinac Bridge after local prosecutors said investigators believed the men were targeting the span.

Local authorities did not say what they believed the men intended to do with the phones, most of which were prepaid TracFones, but Caro’s police chief noted that cell phones can be untraceable and used as detonators.

The FBI issued a news release yesterday saying no imminent danger threatened the bridge linking Michigan’s upper and lower peninsulas.

The release also said the FBI had no information indicating that the men, Palestinian-Americans living in Texas, had any direct links to any known terrorist groups or to the alleged plot to bomb trans-Atlantic jetliners that was disclosed in London last week.

The assistant special agent in charge of the FBI’s Detroit field office, William Kowalski, said authorities believe that concern about the bridge was connected to images of the Mackinac Bridge found on a digital camera belonging to the men.

Mr. Kowalski said buying cell phones in bulk was not illegal but that profits from that kind of activity can be suspicious.

Adham Abdelhamid Othman, 21, of Dallas, and Maruan Awad Muhareb, 18, and Louai Abdelhamied Othman, 23, both of Mesquite, Texas, were stopped by police Friday outside a Wal-Mart store in Caro, about 80 miles north of Detroit, after employees became suspicious when they purchased about 80 cell phones.

Local prosecutors charged them with collecting or providing materials for terrorist acts and surveillance of a vulnerable target for terrorist purposes.

The men told a magistrate Saturday that they were buying the phones for resale.

Louai Othman’s wife, Lina Odeh, told the Associated Press on Saturday that she thought her husband and relatives were targeted because of their Arab descent. She said the men’s families come from Jerusalem.

The Tuscola County prosecutor, Mark Reene, said yesterday that representatives of his office and Caro police had met on Sunday with officials from the FBI, the Department of Homeland Security, and the office of the attorney general. He said all the agencies were working together on the investigation.

Messages seeking further comment from Mr. Reene were not immediately returned.