A major operation by the investigation wing of Income-Tax Department on the diamond companies based at Bharat Diamond Bourse (BDB) at Mumbai's Bandra-Kurla Complex (BKC) on Monday rattled the diamantaires in the world's biggest diamond cutting and polishing centre in Surat.

Sources said the Mumbai I-T department swooped down on more than 17 diamond companies located at BDB. The search and seizure operation was extended to Mahidharpura diamond market in Surat as some of the diamond firms of Mumbai have their offices and units here.

More than 60 I-T personnel along with a team of 100 police personnel swooped down at BDB in Mumbai.

One of the diamond firm is believed to have declared Rs 11 crore income even as the I-T officials seized documents, cash and jewellery from the offices and residences of the diamantaires.