Boulder police are working with the FBI to investigate three robberies -- including two bank heists -- in the city in less than 24 hours that they believe could be the work of the same man.

Still another bank robbery occurred Tuesday evening in Longmont, and police are looking into whether that crime is also linked to the others.

The first Boulder robbery took place at 5:26 p.m. Monday at the Wells Fargo bank at 1690 Canyon Ave. In that case, witnesses told police that a man walked into the lobby of the bank and handed one of the tellers a note demanding money. The man claimed to have a gun, although no weapon was seen.

The teller handed over cash, and the man got away.

The second robbery occurred around 10:45 p.m. Monday at the Circle K gas station at 3185 28th St., according to police spokeswoman Kim Kobel. In that case, the suspect walked up to the counter, asked for a package of cigarettes and then showed the clerk a note demanding cash from the register.

Again, Kobel said, the note said the suspect had a gun, although no weapon was displayed. No one was hurt, and the suspect escaped with an undisclosed amount of cash, she said.

The third Boulder robbery happened at 9:45 a.m. Tuesday. Witnesses at the Boulder Valley Credit Union, 2667 Broadway, said a man handed a note to a teller demanding money and claiming to have a gun. There were no customers in the bank at the time, although several bank employees were inside.

No one saw a gun and no one was hurt, Kobel said. The suspect got away with an undisclosed amount of cash, she said.

He was described by credit union employees as a 40- to 50-year-old white male, about 6 feet tall with pockmarks and acne scarring on his face. He was wearing a dark jacket, tan pants, a brown knit hat with tassels and dark sunglasses.

The Circle K clerk also described the suspect as a white male, about 40 to 50 years old and 6 feet tall. He wore a brown baseball cap in that case and had straight brown hair. His face was pockmarked, according to the description, and he had prominent cheekbones.

The suspect in the Boulder Wells Fargo robbery was described as having a pockmarked face and brown hair.

The Longmont bank robbery was at the Wells Fargo bank in the Safeway at 1050 Ken Pratt Blvd. just after 6 p.m. Tuesday. Police described that robber as a 5-foot-8-inch white man with a skinny build. He was wearing gloves, a blue-green jacket and a beanie-style hat with drawstrings, according to Longmont Police Sgt. Jim Bundy.

The man was seen getting into the driver's side of a white Ford Explorer that was either a late '90s or early 2000s model, Bundy said.

Sgt. Bruce Wittich said the man handed a teller a note saying he was armed, desperate and in a hurry, and wanted all the money in the drawer. The teller didn't see any weapons, Bundy said, and no one was hurt in the robbery. Police did not say how much money was taken.

Longmont police are looking into whether the Safeway robbery is related to the three in Boulder, but nothing had been determined yet, Wittich said.

Detective Brian Scott is the lead investigator on all three Boulder cases. Anyone with information can call him at 303-441-3381. Anyone with information who wants to remain anonymous can call the Northern Colorado Crime Stoppers at 800-222-8477. Tips also can be submitted via the Crime Stoppers website at crimeshurt.com.

Tips submitted through Crime Stoppers that lead to the arrest and filing of charges might be eligible for a cash reward of up to $1,000 from Crime Stoppers.