The Conservative Party conference was temporarily locked down because of a “potential security alert”, police have said.
Delegates were not allowed to enter or leave the event, held at the International Convention Centre (ICC) in Birmingham, for more than an hour on Monday afternoon.
The alert was reported shortly before the chancellor, Kwasi Kwarteng, was due to address the annual conference.
A spokesperson for West Midlands Police said: “Due to a potential security alert we have temporarily restricted access to and from the ICC.”
Shortly after 5pm, the force said security restrictions were lifted, and that delegates and visitors were able to leave.
No further details were immediately given on the reason for the alert.
A crowd was seen gathering outside the entrance to the convention centre as the lockdown continued, with police officers on the scene.
The conference has been protected by an extensive security operation mounted by police and stewards, including bag searches and body scanners.
Protesters have been gathering near the venue, where Jacob Rees-Mogg was chased and heckled on Sunday.
The business secretary faced a hostile reception as he crossed Victoria Square in the city centre, escorted by several police officers.
Conservative MP Michael Fabricant said protesters also “shouted abuse” at him.
West Midlands Police said on Sunday that no arrests had been made in relation to any disorder.
“Thousands of people supporting a variety of causes have exercised their right to protest in the city centre,” a statement added.
