Leeds Teaching Hospitals NHS Trust confirmed that officers are currently at the scene at Chapel Allerton Hospital after a call to police shortly before 3pm.
A West Yorkshire Police spokesperson said: "At 2.57pm today, police received a report of suspect package in a toilet at Chapel Allerton Hospital.
"A cordon has been put in place and the hospital has carried out a partial evacuation while the package is examined."
A Leeds Teaching Hospitals NHS Trust spokesperson said: "A suspicious package has been found and police are dealing with it.
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"Some patients have been asked to leave the hospital by police but we're not sure how many as yet."
It is not known yet which area of the hospital is affected.