Police said Northwestern Memorial Hospital in Chicago was put under a temporary lockdown April 24 after someone made a threatening phone call to the facility, according to NBC 5 Chicago.
The lockdown began about 8:40 p.m. and was over about two hours later.
In a Twitter post, the Northwestern Medicine media relations team said Northwestern Memorial Hospital was placed on an armed intruder alert the evening of April 24.
Hospital security, Chicago Police and Northwestern University Police "responded promptly and confirmed there is no active threat," the team said.
The hospital had resumed normal operations as of 10:23 p.m. April 24.