Portland police are investigating a pair of weekend robberies and exploring a possible connection with a robbery last week at a car wash.

Early this morning, a man wielding a large knife threatened workers at the Domino’s pizza shop at 788 Forest Ave. The man was described as in his early 30s, white, 6-foot-1, and wearing a gray hooded sweatshirt with the hood up, police said.

On Sunday at 3:25 p.m., a man used a large butcher’s knife to threaten a clerk at the Dollar Store at the 449 Forest Ave. plaza. This robber was described as in his early 20s, white, thin build, and wearing a red hooded sweatshirt with the hood up.

Nobody was hurt in either incident.

Police say there are similarities between the two robberies this weekend and one July 13 that occurred at the ScrubaDub auto wash at 1185 Forest Ave.

Police asked that anyone with information call 874-8533.