The UN Convention urges its signatory nations to cooperate in the matters pertaining to corruption, they said.
The CBI move comes amidst media reports that Indian agencies told the Caribbean nation that there was no adverse information against Mehul Choksi when it did a background check on the fugitive billionaire before granting him citizenship in 2017.
According to a statement of Citizenship by Investment Unit of Antigua and Barbuda, published in Antiguan newspaper The Daily Observer yesterday, Antigua has claimed that Indian agencies had not shared any "derogatory information" about Choksi during its background checks.
Choksi's application for citizenship in Antigua in May 2017 was accompanied with clearance from the local police as required by norms, the newspaper reported.
Choksi was granted citizenship in November, 2017 after a detailed "background check" and "due diligence", The Daily Observer had said in an earlier report.
After getting Antiguan passport, Choksi had fled India on January 4 this year and took an oath of allegiance in Antigua on January 15, 2018.
On January 16, this year, the $2 billion scam was detected by Brady House branch of Punjab National Bank, making it the biggest banking scam in the country.