MONROE — Monroe police and the FBI are investigating a brazen take-over bank robbery early Tuesday during which four employees were tied up.

Before the bank was open, a man with a handgun forced his way inside the downtown Monroe branch of Key Bank as an employee was letting herself in.

Once inside, the man, who was wearing a dark, hooded sweatshirt, tied up four employees, all women, and led them to a back room, police said.

“I’m sure that the employees were very scared,” Monroe police spokeswoman Debbie Willis said.

The man was in the bank for about 15 minutes, Willis said. The employees complied with the man’s demands and he made off with an undisclosed amount of cash.

No arrests have been made in the early morning incident. The robbery was unusual, experts said.

Typically, bank robberies occur during regular business hours. People walk up to a teller and demand money, FBI Special Agent Robbie Burroughs said.

Last year, there were 153 bank robberies in Washington. About a dozen were take-overs, Burroughs said.

Nationwide, fewer than 1 percent of the 6,500 reported bank robberies were take-overs staged prior to the bank opening, she said.

Fewer still are the number of times robbers tie up bank employees, Burroughs said.

There have been two other bank robberies in Washington state since late December that occurred prior to business hours.

The FBI doesn’t believe the previous incidents, one near Olympia, the other near Vancouver, Wash., are connected to Tuesday’s robbery.

The Monroe incident was the first time restraints had been used by a robber in Washington this year, the FBI said.

The women were quickly able to free themselves and call 911. No one was physically hurt, but the employees were scared, Willis.

About 9:15 a.m., an hour after police were called, officers found the stolen Ford Explorer about a mile south of the city. The sport utility vehicle was abandoned on Tualco Loop Road near a popular fishing spot, Willis said.

Detectives believe the suspect could have gotten into another car.

There are reports that the souring economy is leading to an increase in bank robberies in other parts of the country.

“We’re just not seeing that here,” Burroughs said. “The only economic crisis that our bank robbers are concerned with is the price of heroin.”

The suspect was described as Hispanic, about 5-foot-6 to 5-foot-8, about 125 pounds.

Anyone with information is asked to contact the Monroe Police Department at 360-794-6300 or leave an anonymous tip at 360-863-4600.