The bridge, which connects central and southern parts of London, was stuck for several hours on Monday, preventing vehicles and pedestrians from crossing the River Thames.
Images from the scene on Monday afternoon showed traffic built up on both sides of the bridge, which is owned, funded and managed by City of London Corporation.
“Due to a technical issue, Tower Bridge is currently stuck in a raised position,” a spokesperson for the corporation told the PA news agency.
“We are working to resolve the issue as quickly as possible.”
However, it is not known how long the bridge will be stuck for and City of London Police has urged the public to avoid the area for the time being.
In a tweet sent at around 3pm on Monday, the force said: “Tower Bridge is currently closed to traffic and pedestrians due to technical failure.
“Please avoid the areas. Updates to follow.”
Transport for London also said on Monday afternoon that movement for motorists was slow on both sides leading up to the bridge.
The 240m-long bridge, which was built by the Victorians more than 100 years ago, is considered one of the world's most famous bridges and one of London's most recognised landmarks.
It was previously closed to the public last August after a mechanical fault led to it being stuck open for more than an hour.
In that instance, engineers fixed the problem and reopened the bridge to motorists the next day.
The bridge was also closed by police for 10 hours in 2005 after a technical problem meant that the arms could not be lowered.
Additional reporting by PA
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