DETROIT -- The Detroit police bomb squad unit was called out to detonate a device placed in a bank's drive-up teller window Thursday morning.

Police say a man in his 30s, wearing a baseball cap, dropped the device, along with a threatening note demanding cash, in the outdoor teller slot at the Standard Federal on East Warren, near Mack Avenue, at about 11 a.m.

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See Authorities Detonate Suspicious Device Local 4 Reports From Scene

"He pulled up to the drive-up, put the device in the drive-up tray," said Terry Booth, of the Federal Bureau of Investigations.

The man fled the scene with about $20, according to Local 4 reports.

One customer and about 12 employees were evacuated from the bank while the bomb squad detonated the device.

Authorities determined the fake bomb was a CB radio attached to a clock, Local 4 reported.

"Bombs look like anything. There's nobody here who could tell you what a bomb looks like," said Sgt. Dan Reed, of the Detroit Police Department.

Police also closed surrounding streets and businesses during the investigation and detonation of the device.

The FBI and Detroit police continue to search for the robber. Anyone with information is asked to contact authorities.