Several people, gagging and teary-eyed, fled the Farragut North Metro station yesterday after a red dye pack from a bank robbery exploded at the foot of the entrance escalator, authorities said. No one was seriously injured.

The bandit, who had just held up the United Bank at 1667 K St. NW, had entered the station when the pack, which also contained a gaseous substance, exploded in a bundle of cash about 1:50 p.m., police said. The robber then fled, leaving the cash behind, said Capt. Geoffrey Hunter of the District police department.

About four people were treated at the scene, emergency workers said. Seven others were treated at George Washington University Medical Center and released, said Amy Pianalto, a hospital spokeswoman.

Lt. Louis L. Carter Jr., of the D.C. Department of Fire and Emergency Medical Services, said some people at the Metro station experienced difficulty breathing, "but once they got in the fresh air, they were better."

The station was closed from about 2 to 2:30 p.m. Trains passed through the station but didn't stop, Metro spokeswoman Cheryl Johnson said.

Patricia Thornton, director of programming and development for the Golden Triangle Business Improvement District, said she arrived outside the Metro station and saw a woman crying, calling for help at a pay phone.

"People were coming out of the station choking," she said. "Some people weren't able to breathe. They were scared. They didn't know what it was. That kind of fear can be overwhelming."

Soon after, police handcuffed a man in the 1000 block of Connecticut Avenue NW and marched him over to the bank to see if employees there could identify him. He was later released, police said.