Westbrook police are investigating an armed robbery at a coffee shop on Saturday morning that may be related to a recent rash of similar crimes in the Portland area.

A man entered the Daily Grind drive-thru, at 820 Main St., shortly before 8 a.m., brandished a handgun and threatened the clerk, before fleeing on foot with an undisclosed amount of cash, according to a statement from Westbrook police Capt. Sean Lally.

The Daily Grind on Main Street in downtown Westbrook.

Lally described the robber as a white male, wearing dark pants, a dark sweatshirt and a dark face mask.

Detectives are investigating the case and are trying to determine if it is related to a recent series of similar robberies in the area.

Four other convenience stores and gas stations in Greater Portland have been robbed since Tuesday. One of them was another robbery in Westbrook – on Thursday afternoon. In all cases a man entered the stores with a handgun and a face mask and demanded cash, according to police. No one has been hurt in the holdups.

The first robbery was Tuesday night at the Riverton Gas Station on Forest Avenue in Portland. The robber had a silver handgun and was described as a man about 30 years old, 5-foot-5 with a thin build and wearing a heavy dark jacket, dark gloves, and a ski mask.

On Wednesday, Falmouth police searched for a man who flashed a gun at the Lil’ Mart store on Route 1 around 8 p.m., then fled with some cash. He was described as white, wearing a gray hooded sweatshirt, face mask and black gloves.

A white man robbed the Good Things Variety on Saco Street in Westbrook around 1 p.m. Thursday. Police unsuccessfully tracked the robber with a dog. He was described as 5-foot-8, with a skinny to medium build and wearing a blue sweatshirt or fleece vest with yellow lettering, a face mask and sunglasses.

Cumberland police said someone robbed the Irving gas station a 174 Main Str. at 8:44 p.m. Thursday.

Police departments from the four communities met Friday to discuss the investigation and share information but have not said they are looking for the same suspect in all four robberies.