Police were called at 10.26pm on Tuesday, 25 August to reports of a firearm seen.
Local officers and an armed response unit attended and stopped a vehicle at Horsley Street, SE17.
During the search of the vehicle a hand gun was recovered which is believed to be an imitation firearm
Four males, aged 15, 28, 27 and 28 were arrested on suspicion of being in possession of a firearm.
The suspects were taken to a south London police station where they remain at this time.
There were no reported injuries. Enquiries continue.
Anyone with information should call police on 101 or Tweet @MetCC quoting 7815/25AUG. To remain anonymous call Crimestoppers on 0800 555 111 or visit Crimestoppers_uk.org.