Two young men were injured in a night explosion inside a house in Likoni on Sunday night.
Police suspect the two men were assembling a liquid-based improvised explosive device in the kitchen which accidentally went off at around 10pm, wounding the young men.
Anti-terrorist police rushed to the scene and later arrested one suspect and parents of the other who escaped.
And police have launched investigations following intelligence reports that a terrorist act intended for last weekend was disrupted.
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While teenagers, the two suspects were arrested during the raid on Musa Mosque in Mombasa on February 2, 2014, in which six worshipers and a policeman were killed.
"We have received reports one of them was jailed for three years and another four years and we are investigating that," said Likoni OCPD Benjamin Rotich yesterday.
Witnesses told The Standard that a loud explosion went off within the Swabrina neighbourhood in Likoni sparking panic. Police officers arrived at the scene within half an hour.
Within minutes of the explosion, the two men were rushed to a local private hospital while bleeding profusely.
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Mr Rotich said detectives have not established the materials used to make the explosive or what exactly happened. But he indicated that parents were detained on suspicion they had tampered with the scene by washing away blood stains and carting away some material before the police arrived.
The two suspects were first rushed to a private dispensary and then moved to Likoni District Hospital.
Detectives told The Standard the two were first treated at a private facility and transferred to Likoni District Hospital after officials at the private institution demanded certain answers. At the district hospital, they were subjected to questions that prompted their transfer.
Reports indicate one of the suspects vanished thereafter.
Rotich said the other suspect was treated and released yesterday morning to anti-terrorism police for further grilling.
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According to detectives, he told investigators unknown people threw a grenade into their room but police rejected the theory.
Yesterday morning, 20 anti-terrorism police officers, accompanied by GSU and intelligence teams sealed off the site for investigations.