PLEASANTON -- Police are searching for a group of men suspected of working together to rob area pharmacies by demanding narcotics and claiming to be armed, police said.

Four similar attempted robberies were reported within 36 hours at pharmacies across Dublin and Pleasanton, police said. Though the suspect descriptions vary widely, the robberies are similar in nature, which suggests to investigators that the suspects may be working together.

Pleasanton police responded to the Rite-Aid store at 2819 Hopyard Road about 12:38 p.m. Thursday, after a 911 caller told dispatchers that a man had handed the pharmacist a note demanding prescription narcotics that also stated he had a gun, Pleasanton police Lt. Brian Laurence said.

The pharmacist did not give the man any drugs, and the man left the pharmacy without showing a weapon, Laurence said. The man was last seen in front of the Rite-Aid about 12:40 p.m.

The suspect is described as a white male about 30 years old, standing 5 feet, 3 inches tall and weighing 150 pounds. He was wearing a light brown jacket and a brown beanie and is described as having a very red face and a scruffy beard.

In Dublin, a suspect presented a similar note to the pharmacist at the Safeway on 7499 Dublin Blvd. at 12:38 p.m., police Lt. Herb Walters said. No weapons were produced or injuries reported, though the suspect did make off with several bottles of hydrocodone.

The same suspect attempted to rob a CVS pharmacy at 7201 Regional St. in Dublin about 5:50 p.m. Wednesday, Walters said. A note that read "This is a robbery" was presented, though it did not make mention of a gun. The suspect ran from the store after he thought the employee pressed an alarm button.

That suspect is described as a white male, about 5 feet, 7 inches tall and weighing 225 pounds, Walters said. He was last seen wearing a gray sweatshirt and gray beanie.

Another attempted robbery occurred in Pleasanton at 6:15 p.m. Wednesday at the Lucky pharmacy at 6155 W. Las Positas Blvd., Laurence said. In that robbery, a man also presented a demand note for opiate-based prescription narcotics and claimed to have a gun.

That suspect also left the store without any drugs, Laurence said. No weapon was seen, and nobody was injured during that incident.

The suspect who attempted to rob the Lucky store was described as an unshaven white or Middle Eastern male, 30 to 40 years old, 5 feet, 8 inches tall and 190 pounds. He was wearing a blue shirt and gray sweatpants.

Anyone with information about these incidents may call the Pleasanton Police Department at 925-931-5100, Dublin police Sgt. Yesenia Sanchez at 925-833-6682 or Dublin Detective Alan Dumatol at 925-833-6684.

Contact Erin Ivie at eivie@bayareanewsgroup.com. Follow her at Twitter.com/erin_ivie.