Oceanografia, which was once Latin America’s largest oil and gas company, valued at more than $3.5 billion, collapsed in 2014 after defaulting on loan payments.

Citigroup allegedly gave Oceanografía a $585 million credit line, allowing it to obtain millions of dollars in cash for invoices for work supposedly done for Mexico’s state-run oil giant Petróleos Mexicanos (Pemex).

However, in 2014, Pemex informed Citigroup that $400 million worth of Oceanografia invoices had been forged.

The bank then canceled Oceanografía’s line of credit and the company went filed for bankruptcy.

On Monday, Oceanografia filed a lawsuit against Citibank in a Manhattan federal court, claiming that Citibank had profited from the fake invoices and had used Oceanografía as a scapegoat.

Citibank has denied those allegations, claiming that the case is without merit and that Oceanografía is simply trying to cash in on the bank’s assets when it is about to be sold.