Scores of armed police were deployed to east London after men in a car were reported to be carrying a gun.
Dramatic pictures show weapon-carrying officers on the scene on Burdett Road in Mile End - as the incident unfolded around 5pm.
A Metropolitan Police spokesman said they were called at around 4.50pm to reports of males seen in a car who were believed to be in the possession of a firearm.
He said armed officers attempted to stop the vehicle, adding: "The car failed to stop for police. This car was in a collision with another vehicle. The occupants abandoned the car and attempted to flee the scene.
"Armed officers detained three suspected occupants from the car. There is a scene in Burdett Road with ongoing associated road closures.
"There has been no firearm recovered at this time and inquiries continue. No shots were fired."
Pictures shared on social media show a battered silver vehicle at a stop in the middle of a police cordon, which has resulted in traffic and buses being diverted.