A pipe bomb was recovered from the outskirts of Madurai on Saturday, the route which was to be taken by Bharatiya Janata Party leader L K Advani on the second leg of his yatra.
The five-feet long bomb, linked to a 50-metre wire and four detonators and batteries, was found under a culvert at Alampatti near Tirumangalam, 30 km from Madurai, said the police.
One person, identified as Nehru, has been detained for interrogation, said the police.
"We are yet to analyse the explosives packed in the pipe," they said.
Advani, who has the highest "Z-plus" category security, was on his way to Srivilliputhur via Tirumangalam. Now, he would take a circuitous route via Virudhunagar and Sivakasi, police said.
Suspecting it could be the handiwork of Naxals, who allegedly have a base in the nearby hills in Madurai and Theni districts, police said the crude bomb was powerful enough to destroy the culvert.
They said local villagers, who saw the wires jutting out, informed the police. "But for the people's information, the bomb would have exploded. In total, four detonators and batteries had been linked to the pipe bomb," police said.
The Bomb Disposal Squad and experts arrived immediately to check the nature of the bomb.
Advani started his second leg of the anti-corruption yatra from Madurai and is scheduled to reach Kerala via Srivilliputhur Tenkasi and Shencottah.
In 1998, a series of blasts rocked Coimbatore hours before Advani was to address an election rally, in which 58 persons were killed and over 200 injured.
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