West Yorkshire Police said last night that search teams had found the body of a girl in the water at Paris Gates.
Ursula's family had been told about the discovery, but a formal identification was yet to take place.
The schoolgirl had been reported missing at around 3.45pm that afternoon and a public appeal for information on her whereabouts was issued a few hours later.
Giving an update today on the investigation, a police spokesman said: "Following the discovery of a body in the River Calder at Paris Gates in Halifax yesterday police can confirm that 11-year-old Ursula Keogh was found deceased.
"Police are working to establish the full circumstances and will prepare a file for the coroner.
"Her family are being supported by specialist officers and have requested for privacy at this extremely difficult time."