Portland police block off Congress Street near Congress Square on Saturday afternoon. Aimsel Ponti photo

A 10-year-old armed with a pellet rifle styled to look like an assault weapon alarmed passers-by and triggered a major police response Saturday in the heart of downtown Portland.

Witnesses on Congress Street flagged down Portland police officers around 3 p.m. and reported that a group of people were firing off an “AR-style” weapon toward passers-by, police spokesman David Singer said.

People told police the group was in a nearby vehicle and officers made a high-risk traffic stop, Singer added. During the stop, a gel pellet rifle was confiscated from a 10-year-old from Lisbon, Singer said. No arrests were made and the incident is under investigation, he added.

An eyewitness to the scene reported multiple police vehicles and officers at the area, near Congress Square. Some lanes of traffic were blocked during the incident, according to photographs provided to the Press Herald.

The Congress Street incident comes a day after Portland police urged caution about realistic pellet guns. Some companies produce air rifles and pistols that look identical to the type of weapons used to kill adults and children in mass shootings, including recent massacres in Buffalo, New York, and Uvalde, Texas.

A BB gun styled to look like a Glock pistol and attached with a laser sight was confiscated from a 17-year-old by Portland police last week after the teen was observed aiming the sight at people.

The guns pose a safety risk to officers and residents due to the obvious fact they could be mistaken for real weapons, the police department said.

“The department urges parents and guardians to monitor the purchase, use and display of these weapons in any situation where they could be perceived as a threat,” it said.

Police departments across the country have issued similar warnings about replica guns in recent weeks.