In a rather candid disclosure, a top Income Tax official has admitted that the diamond trade has one of the highest prevalence of black money, with investigations revealing that books in the sector are "completely manufactured".

"(In) certain areas like real estate or diamond trade there is a lot of circulation of black money...but in the case of diamond merchants, the books are completely manufactured," Director General of Income Tax (Investigations), B P Gaur, told reporters here late last evening.

In the case of the diamond trade, there may be a "complete mismatch" between what "is the real transaction and what is being shown in the books," which makes the job of the Department very difficult, he said.

"It requires very deep investigations to find out the truth," Gaur said.

Tracking the black money trail in the realty sector, also notorious for black money transactions, has, however, been easier for the I-T authorities as it has been able to collect evidence in different forms like computer hard disk drives of the assesses.

The DG was speaking in presence of the Central Board of Direct Taxes member, Prakash Chandra, after the unveiling of a reference book for I-T officials which explains the 'dos and dont's' while carrying out an assessment or investigation with sector-wise real-life cases as examples.