New Delhi: The Central Bureau of Investigation (CBI) on Thursday sent fresh summons to billionaire jeweller Nirav Modi and his uncle Mehul Choksi to join the PNB fraud investigation as early as possible and made it clear to the duo that they were “obliged" to cooperate, officials said.

The agency had sent three summons on 19, 23 and 28 February asking them to join the PNB fraud probe at the earliest. They were asked to appear on 7 March.

Gitanjali Gems Ltd promoter Choksi, in his seven-page letter which was released by his lawyer, has said it was impossible for him to return to India and join the investigation due to the suspension of his passport and ill-health.

In a detailed email reply to the CBI’s notice seeking his appearance, Choksi said his passport has been suspended by the authorities and he was undergoing medical treatment. He said that on 16 February he received an email from the passport office which stated that his travel document has been suspended due to the reason “Security Threat to India".

However, the Regional Passport Office in Mumbai, did not give him any explanation for suspension of his passport or as to how he was a security threat. “I am also not in a position to travel due to my persisting health problem. I had a cardiac procedure which was conducted in the first week of February 2018 and there is still pending work to be done on the same. The entire procedure could not be completed on all veins due to danger to kidney and therefore I am not allowed to travel for at least a period of four to six months," he said.

A response on similar lines was received from Nirav Modi citing that he could not travel to India to join the probe. In a terse reply, CBI “directed" him to approach the Indian mission in the country where they were residing so that immediate arrangement can be made for their travel to India, officials said.

The CBI wants Modi and Choksi to join the investigation related to the $2 billion PNB fraud pertaining to fraudulent issuance of the LoUs from the bank’s Brady House branch in Mumbai in their favour.