The Met Police were called to the fast food chain on Balham Hill, Clapham, at around 7pm. Diners were ordered to leave the premises as a specialist team were called to the scene.
Surrounding areas have been cordoned off by the police.
The road closures has caused delays in both direction on the A24.
Independent station, Radio Jackie tweeted: “#Clapham Queueing traffic due to earlier police on A24 Balham Hill in both directions from B237 Nightingale Lane ( Clapham South Station) to Yukon Road.
“All lanes have been re-opened. Police closed the road while they attended to a suspect package.”
The Met Police has been contacted for more information.
This is a developing news story, more to follow.