LIVERMORE — Investigators are working to confirm identities of four people arrested on suspicion of armed robbery, authorities said.

Around 1:10 p.m. Thursday, three masked suspects walked into T-Mobile, 4516 Las Positas Road, and one pretended to have a gun, police said. After one of the store’s two employees managed to get outside and told a passerby of the robbery attempt.

The three suspects then ran out of the store to a newer-model white Jeep Cherokee driven by a fourth suspect, who fled west along Las Positas. An officer nearby found the Jeep and followed it to the dead-end of Old First Street, where three fled the vehicle into the surrounding neighborhood.

Officers responded to the area, arresting the Jeep’s driver and eventually detaining the last of the three others by 4:45 p.m. after a search with air support from the East Bay Regional Parks police and two K-9 officer teams from the Alameda County sheriff’s office.

Although the suspects had not been named, police said they believed they were gang members out of Fresno. Anyone with information should call Livermore police at 925-371-4777.

Contact George Kelly at 408-859-5180.