A fourth person has been arrested in connection with the death of a 58-year-old man more than two years ago.
Stephen Pollard's body was found on the banks of the River Aire in Beale, North Yorkshire on 22 May 2015.
Police said at the time his death was not treated as suspicious, but new information had since come to light.
A woman, 51, from York, is being held on suspicion of assisting an offender. Three men arrested on Wednesday on suspicion of murder have been bailed.
Police said Mr Pollard was reported missing from his home in Wakefield on 27 February 2015.
His vehicle was discovered by officers in Wakefield on 5 March before his body was found later that month.