What is the relationship between Banamex and Citigroup in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

Citigroup has faced a number of probes over Banamex after it announced a charge of about $235 million in February 2014 due to uncovering "significant" fraud on the books of oil contractor Oceanografia after having lent it $585 million through a Banamex unit.

Answer: operator