French officials have launched a formal investigation into a Muslim cleric suspected of having links to the would-be shoe-bomber Richard Reid, judicial sources say.

The move against Kamel Lakhram, the imam or prayer leader of a mosque north of Paris, allows investigators to continue their inquiries and decide if he should be charged.

Police want to know who Reid knew in Paris

French authorities have been trying to establish what logistical or financial help Reid had before he boarded a Paris to Miami flight in December 2001 and tried to detonate explosives hidden in his shoes.

The mosque leader was one of eight suspects police arrested last Tuesday by French police investigating Reid's activities. The other seven - detained in a mosque, prayer hall and restaurant - have been released.

Two other recent raids netted 11 other suspects, most of whom have also been freed.

Suspicions

As well as looking for anyone connected to Reid, the French are trying to uncover any broader networks of Islamic militants, judicial sources said.

They also want to know what the would-be bomber was doing in Paris in the days before he boarded the plane bound for Miami.

Reid, 29, pleaded guilty in October in a US court to trying to blow up the flight and declared himself a disciple of al-Qaeda leader Osama Bin Laden and an enemy of the United States. He will be sentenced in January by a US court.

His attempted sabotage was thwarted when he was spotted by a flight attendant trying to ignite a small amount of explosives hidden in the hollowed-out heel of his shoes.