Citigroup Inc. was used for fraud by investors and creditors in a Mexican oil services firm over claims they were harmed by a loan scheme that led the bank to cut 2013 profit by $235 million and fire at least a dozen people.

The bank’s actions caused Rabobank Groep and other investors and creditors of the Mexican firm to lose at least $1.1 billion, according to a complaint Friday in Miami federal court. Rabobank and other investors also filed a separate negligence lawsuit in state court in Delaware against auditor KPMG LLP. The law firm Quinn Emanuel Urguhart & Sullivan LLP provided copies of the complaints, which couldn’t be independently confirmed with the courts.

David Voreacos and Dakin Campbell