Vauxhall Bridge in central London was closed at rush hour while armed police probed an abandoned vehicle.
Officers rushed to the scene at around 4pm and closed the bridge after receiving reports of a suspicious vehicle.
Police later said the abandoned car had been assessed and was deemed non-suspicious. The bridge reopened at around 6.15pm.
In an earlier statement, Met Police said: "Police are in attendance in Vauxhall Bridge after a vehicle was found abandoned just before 4pm.
"The abandoned vehicle is being examined by specialist officers as a precaution. No arrests have been made."
Police also closed Vauxhall station due to the "security alert", with one witness saying the area is "swarming with police".
Nearby theatre Above The Stag was also evacuated, according to reports.
South Western Railway said trains would not be stopping at Vauxhall "until further notice", adding that tickets would be accepted with Southern between Clapham Junction and Victoria.
Footage from the scene showed a tow truck arriving at the scene.
A police spokesman added earlier: "Vauxhall Bridge will remain closed whilst the vehicle is assessed by specialist officers.
"Buses will be diverted and members of the public are advised to avoid the area."
