PARK RIVER (AP) - A flurry of crimes has FBI investigators busy in northeastern North Dakota.

The robbery of the Gate City Bank in Park River on Thursday was the fourth FBI-investigated bank robbery this year in North Dakota, and the third in the northeastern part of the state.

Paul McCabe, an FBI spokesman in Minneapolis, said no suspects have been identified in robberies last month of Ramsey National Bank and Trust in Devils Lake or the Bremer Bank branch in Grand Forks.

The FBI also is investigating the heist of a bank-owned cash machine from a convenience store in Drayton last month. Authorities said the heist was similar to earlier after-hours ATM burglaries in Minto, Grand Forks and Fisher, Minn.

The three previous ATM burglaries involved store-owned cash machines and did not lead to FBI investigations. However, McCabe said the agency is checking into any possible connections among recent bank and ATM thefts and other crimes.

McCabe said it is not clear if the number of bank robberies is above the norm for North Dakota. Last year, there were only three bank robberies in the state, but in 2001 there were six, he said.

"It can really vary, and it's really hard to determine what causes it to fluctuate like that," McCabe said.

There typically is some connection to illegal drugs behind bank robberies in the region, he said.

"That's followed, secondly, by a gambling problem. And the next in line is they just want or need the money," McCabe said. "But the majority of the cases we've seen seem to have a drug nexus."

The last time there was a bank robbery in Park River, a Walsh County town of about 1,600 people, was Nov. 16, 1931.

Bart Hankey, who was 7 at the time, and his wife Irene, who was 5, remember the incident.

"We kids were so excited," Irene Hankey said. "We lived along the highway and we waited outside for the robbers to come by, but nobody ever did. Finally, mother called us in for lunch."

The robbers eventually were caught in South Dakota and sentenced to 30 years in prison, according to the town's centennial history publication.

Bart Hankey was in a hardware store Thursday morning when Gate City was robbed. He heard the store manager announce the news. From there, it just traveled like wildfire," Hankey said. "I think people will be locking their doors and taking the keys out of their cars now."