A woman described as “erratic and aggressive” drove a vehicle into a US Capitol Police vehicle near the Capitol and was taken into custody, police said.
Shots were fired, but the incident appeared to be criminal in nature with “no nexus to terrorism”, said Capitol Police spokeswoman Eva Malecki.
No one was injured. She said the US Capitol remained open.
Ms Malecki described the woman as an “erratic and aggressive driver”.
The incident occurred near the Botanic Gardens.
A District of Columbia police spokeswoman, Margarita Mikhaylova, said it is possible that an officer fired shots, but the Capitol Police spokeswoman declined to elaborate.
DC fire department spokesman Doug Buchanan said ambulances were sent to the scene, but did not take anyone to the hospital.
Earlier, a witness said a car was stopped at a checkpoint and police ordered a woman driving a vehicle to stop.
The incident prompted a large police response. Streets near the Capitol were closed.
Almost exactly one year ago, US Capitol Police shot a man after he pulled a weapon at a US Capitol checkpoint as spring tourists gathered in Washington.
The suspect was previously known to police, who last October had arrested him for disrupting House of Representatives proceedings and yelling he was a “Prophet of God”.