A Nariobi court has ordered the six to be detained for 30 days while police investigate a possible connection to last week's attack.
The court agreed to lawyers' request for the extended detention period, which usually would last 24 hours before the detainee has to be presented in court.
Lawyers for the arrested said they were being investigated for supplying weapons to the attackers. One man was attested on the campus where he worked as a security guard, the others were detained whilst trying to cross into Somalia.
Yahoo news reported that one man was found 'hiding in the ceiling' of the campus holding grenades, according to the interior minister Mwenda Njoka.
Police are studying phone records of the men to see if they were in contact with the four gunmen who were killed by Kenyan troops after carrying out the attack.
On Sunday authorities named one of the four gunmen killed as a Kenyan citizen, showing the militant group al Shabaab is recruiting internally.
It's been increasing attacks inside Somalia as well as recruitment in the north eastern and coastal parts of Kenya.
A $215,000 bounty has been offered for alleged commander Mohamed Mohamud, a former Kenyan teacher believed to now be in Somalia and said to be the mastermind behind the Garissa attack.
