A 44-year-old man was arrested Tuesday night on suspicion of planting an explosive device in the bathroom of a Starbucks coffee shop, police said.

Ronald Schouten, of San Francisco, was being held in San Francisco County jail on an unrelated drug charge, police spokesman Dewayne Tully said.

"There is no connection to any terrorism or anything against Starbucks," Sgt. Neville Gittens said. "Everything at this point and time indicates that this particular individual acted alone and this is an isolated incident."

An employee called police Monday morning to report something suspicious in the store's bathroom. Police evacuated the store and disabled the device.

Police said the bomb was powerful enough to seriously injure or kill someone if it had exploded.

Police evacuated roughly 100 people from the Starbucks and apartments above the store and shut down traffic on the street.

The store reopened Tuesday, but the restroom remained closed.