Westminster Bridge was shut while Metropolitan police responded to a “security alert” at St Thomas’ hospital in London.
The Metropolitan Police said there were no reports of injuries during the incident on Tuesday morning, which saw members of the public evacuated from the surrounding area.
Around half an hour after the security alert was announced, police said it was being stood down.
Officers were called at around 9.20am following reports of a man making threats, Scotland Yard said.
No weapons were seen but armed officers attended as a precaution and surrounding roads were closed.
A spokesperson for the Metropolitan Police said the hospital was not evacuated, adding: “Officers subsequently located and spoke to a male inside the hospital. The incident was stood down at approximately 10.30am.
“There have been no arrests and this was not treated as a terrorism incident.”
Westminster Bridge was the scene of the first terror attack claimed by Isis in the UK, in March 2017, and a car ramming in Parliament Square in 2018 was also declared a terrroist incident by police.
Witnesses reported seeing armed police near an expanding security cordon around the hospital, which sits on the south bank of the River Thames, next to Westminster Bridge.
A spokesperson for the Guy’s and St Thomas’ NHS Foundation Trust could not immediately provide further information on the incident.