Dyfed Powys Police say they are not looking for anyone else in connection with the deaths of a that a mother and daughter who were found dead at their home in Builth Wells on Monday.
In a statement the force said they do not believe they died from carbon monoxide poisoning.
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More than a thousand riders will be taking part in a series of events in and around the town.
Some warm spells of sunshine will develop, although scattered heavy and thundery showers are also expected during the afternoon.
A yellow 'be aware' warning has been issued by the Met Office for much of Wales.