Three more men are being questioned in connection with the murder and robbery of Dr Louis Heyns, Western Cape police said on Thursday.
Captain Frederick van Wyk said the men, between the ages of 22 and 29, were arrested late on Wednesday.
He said one of them was a police official but he could not reveal his rank.
Three men have already appeared in court in connection with the crimes.
Marthinus van der Walt, 33, his brother Sarel, 42, and Malmesbury businessman Juan Liedeman, 37, appeared in the Somerset West Magistrate's Court on Monday.
The Cape Times reported that the brothers were told they would be charged with murder and robbery, while Liedeman faced a robbery charge.
According to the newspaper, the charge sheet stated Heyns had been kicked and hit with fists near De Beers Avenue at Somerset Mall on May 22.
The charge sheet reportedly stated further that, in the same vicinity, he had been robbed of his vehicle, a gold ring, a cellphone, a pair of takkies, and two cards.
His body was found in a shallow grave in Strand a week ago.
Liedeman would apply for bail in the Western Cape High Court later on Thursday.
National Prosecuting Authority Western Cape spokesman Eric Ntabazalila said they intended opposing the application.
The case would resume in the Somerset West Magistrate's Court on Monday.
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