The CBI conducted searches at the local residences of at least six customs officers early on Thursday, a day after seizure of unaccounted money from some officials at the international airport in nearby Nedumbassery.
In the raid at the airport, which continued late into the night, the CBI seized USD 300, 200 Dirhams and Rs 10,000 from customs officers. Thursday's searches were a follow-up to this, sources in the probe agency said.
However, no arrests have been made.
Following complaints from passengers that customs officers at the airport were seeking bribes, the CBI had 10 days ago requested Central Industrial Security Personnel (CISF) to record through closed circuit television the activities of suspect customs officers at the airport.
It was found that in several instances, customs officers had taken bribes, the sources said. Thursday's raids were conducted after a case was registered in the matter.
In a similar exercise, CBI had conducted a series of raids at customs wing of Karipur airport near Kozhikode last year.
Investigations in the case were over and the Central agency was awaiting sanction to launch prosecution proceedings against 32 customs officials, including an Assistant Commissioner.
It had recommended departmental action against 23 other customs personnel in connection with a racket involving systematic collection of bribes from passengers arriving from Gulf countries through the airport.