Anti-terror detectives were on Sunday interrogating a man who has been creating illegal explosive devices, including the bomb found with a pastor on Saturday.
The 24-year-old man was arrested at his house at Kibichoi village in Gatundu, with explosives and other materials enough to assemble 10 bombs.
Police stormed the house at around 7 pm on Saturday, five hours after arresting the pastor.
Ten detonators, a sack with fertilizer weighing about 10 kilograms, and rolls of cables were found after the police ransacked the house.
They were led to the home by a man identified as a quarry worker who was arrested together with the pastor when a vehicle they were travelling in was intercepted at the Runda tunoff on Kiambu Road.
During interrogation, he told police that his clients are quarry workers who use his improvised devices for excavation.
He did not have a licence allowing him to trade in explosives as required by the law.
A fourth man is being sought after the bomb maker named him as the one who supplies him with materials from Nairobi.
Police suspect the bomb was intended for criminal activities and were interrogating the pastor to establish where he intended to use it.
The arrests were made by Special Crimes Prevention Unit detectives who then handed over the suspects to colleagues at the anti-terrorism unit.
The latter has been spearheading investigations into Uhuru park explosions in which seven people died, but had made little progress.
They had established three devices were used, a Russian made grenade and two Improvised Explosive Devices (IEDs).
Faithful had gathered at the park for a prayer meeting called by the church but had turned into a campaign rally against the proposed Constitution.
The quarry worker told police that the pastor approached him, saying he wanted some work done.
He also told police that he helped the pastor acquire the explosives but did not know where they were headed to before being arrested.
The two were travelling towards Nairobi when the vehicle was intercepted.
In Mombasa, security was on top gear since Friday, ahead of Sunday’s “No” campaign rally at Tononoka grounds.
A senior government official told the Nation intelligence reports at the Coastal town had warned of a plan to “disrupt the rally” but without details of how it would have been done.
Concerning the arrests, police spokesman Eric Kiraithe said: “One Pastor John Kamau of Mission Church Githunguri and an accomplice Samuel Chege Gitau were arrested and substance believed to be prilled ammonium nitrate, a detonator and a safety fuse were also recovered from them.”
“The two suspects are now under investigation to establish their motive and identify any other accomplishes,” he added.
He also assured the public that police are taking measures to ensure law and order is observed during the referendum campaigns and on the voting day.
Other intelligence reports had revealed of plans to disrupt the process.
Roads minister Franklin Bett said: “Am disturbed if we as a country are reaching a state where people of collar are arrested with dangerous weapons. We need to do a lot of soul searching.”
He wondered if the pastor could be linked to the Uhuru park blasts.
The minister also asked the police to investigate the incident thoroughly, so that culprits are not freed for lack of evidence.
“Is this person actually a pastor? We’ve to get to the bottom of this,” Mr Bett added.
The arrests occurred barely 24 hours after an exposé by the Nation, showing how easy it is to assemble a powerful bomb.
For Sh1,000, the Daily Nation bought enough material to make a bomb powerful enough to blow up a large room though the sale of such substances is supposed to be tightly controlled in law.
Leading bomb expert Charles Juma had indicated a non-electric detonator, a length of safety fuse and half a kilo of top-grade fertilizer would be enough to make such a bomb.