Seven robbers tied up two employees and stole money out of the cash register early Wednesday at an upscale restaurant along San Francisco's waterfront, police said.

The holdup happened at Chaya Brasserie at 132 The Embarcadero at 12:15 a.m., after the restaurant had closed, police said.

The robbers burst in through a side door, assaulted a restaurant manager and custodian and tied them up, said police Sgt. Wilfred Williams. No customers were inside, police said.

One of the assailants was armed with a knife, police said. The men took an undisclosed amount of money from the cash register before fleeing.

No arrests have been made. The robbers were wearing hooded sweatshirts and had their faces covered, so police do not have a good description of them.