South Wales Police says a body has been found in the River Ely, near Penarth Road in Cardiff.
Formal identification has not yet taken place.
The family of 34-year-old Ben Thompson from Haverfordwest, who has been missing for more than a month after watching Wales play in the Six Nations, has been informed and are being kept updated by family liaison officers.
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Variable cloud and clear spells overnight with isolated showers mainly in the north.
Becoming drier and brighter from the northwest during the day, but with the risk of scattered, locally heavy, showers developing later.