Magistrate Mohd Zaki Abd Rahman extended the remand of the four for six more days from today.
Investigating officer DSP Hamzah Buman said the suspects, aged between 21 and 35, had been remanded previously for seven days.
Section 117 of the Criminal Procedure Code provides for a suspect to be remanded for up to 14 days to facilitate an investigation.
Shaharuddin was gunned down in April last year while on the way to his office in Putrajaya.
Two men on a motorcycle fired three shots when the car carrying Shaharuddin stopped at a traffic intersection from Lebuh Sentosa to Lebuh Wawasan.
One of the four suspects is represented by lawyer Datuk Suraj Singh.
On July 6, the Magistrate’s Court issued a six-day remand order on a 20-year-old wireman for a similar investigation.