Victoria Hospital at London Health Sciences Centre went into a partial lockdown due to a bomb threat on Tuesday night.
According to an internal hospital email, the threat came from outside the hospital and London Police are investigating.
"Currently, we are working with our police partners to determine the credibility of the threat. However, out of an abundance of caution we are moving into a partial lockdown at Victoria Hospital. We are still accepting patients, providing care, and are dedicated to ensuring the safety of all patients, visitors, staff, and physicians," said a statement from LHSC.
Calls to London Police were not returned on Tuesday night.
The internal email, sent by Children's Hospital President Nash Syed and obtained by London News Today, said security staff has been posted at hospital entrances.
"Staff and physicians are NOT required to take action at this time. We apologize for the inconvenience, but we are committed to ensuring the safety of patients, staff, and physicians," Syed's note said.
LHSC confirmed the lockdown was lifted at 12:30 a.m. on Wednesday.