Members of the banned CPI (Maoist) outfit laid lethal explosives on the patrolling path in the jungle targeting the Thunderbolt commandos at Makkimala, said police in an FIR submitted in the court on Thursday.

The forest department field staff spotted the explosives on Tuesday afternoon and informed the police. Police suspect the trap was set to avenge the killing of a Maoist cadre in a combing operation.

A case has been registered at the Thalappuzha police station under sections of the Explosives Substance Act and the Unlawful Activities (Prevention) Act (UAPA).

The explosives recovered include eight gelatin sticks coded 'SUN 90', four connected electric detonators, and a steel container filled with other lethal explosives, according to the FIR.

Forest watchers call the spot where the explosives were recovered the Kodakkad region, which is almost 1.5 km from the forest border. The buried explosive was found near the gate of the electric fence set up by the forest department. Police suspect Maoists were behind the recovery As the area is a regular patrolling route of the Thunderbolt commandos.

The Bomb Detection and Disposing Squad (BDDS) from Kozhikode examined the explosives on Wednesday and disposed them of after collecting samples. Later the team examined the entire area and also recovered abandoned explosives including 10 corroded gelatin sticks, one electric detonator, plastic wire, steel nails, powdered white stone used in bomb-making, plastic ropes and damaged pages of newspapers, believed to be used to carry the explosives.

Meanwhile, various agencies, including the anti-terrorist squad and various state and Central government agencies, have joined the probe, it is learned.

Mananthavadi DySP Bijuraj P, the investigation officer, said the investigation is focussed on the Maoist cadres and sympathisers of the area. "So far there have been no leads to pinpoint the accused involved," he said.