Five people have been nabbed in connection to the gun attack in Kenya's Garissa University, which killed 148 people, sources said.
The arrests came after authorities announced a reward of 148,370 pounds for the capture of alleged mastermind, former teacher Mohammed Mohamud, reported Sky News.
About 79 people were injured during the attack, in which Somalia's Al Shabaab militants targeted Christians.
Reports claimed that the masked gunmen were wearing suicide vests and were armed with AK-47s.
Interior Minister Joseph Nkaissery said that the militants "exploded like bombs" as the siege ended. Some officials were wounded by shrapnel.
However, it is unclear if the militants detonated their suicide vests as police approached or they went off on their own after being hit by bullets.
The attack was the worst since Al Qaeda blew up the U.S. embassy in Nairobi in 1998, killing more than 200 people.
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The 12-hour-long-long siege ended as the four gunmen were killed and one suspect was arrested.
Al Shabab said that the attack was in retaliation for Kenya sending troops to Somalia in 2011 to fight the extremists and stabilise the Mogadishu government.