Mexico has declared the data related to its annual oil hedge to be a state secret, Bloomberg reported on Monday.
The Ministry of Finance will keep the data secret for five years, it told the country's auditing body, according to official documents seen by Bloomberg.
This means that the Mexican government will further hold back on information related to what is described as the largest oil transaction on the Wall Street annually -- an already secretive deal.
Mexico hedges against the possibility of rise in oil prices every year with put options, as it seeks to secure one of its largest revenue sources in the state-owned oil company Petroleos Mexicanos, better known as Pemex.
The government has previously said that its intention with holding back information is to lower the speculations and chance of other entities buying the same financial instruments that the government intends to buy ahead of it, thereby increasing the price of the asset.
The finance ministry announced earlier this month that it has hedged its oil for 2020 at $49 a barrel. Mexico had hedged the oil for 2019 at $55 a barrel.
Ther government gave the approximate cost for purchasing the financial contracts for the year at $1 billion, without divulging further details, as noted by Bloomberg.
Exactly which banks are involved in the transaction remains unknown, but some of the previous participants have included Barclays p.l.c., Goldman Sachs Group Inc. (NYSE: GS), Morgan Stanley (NYSE: MS), and Deutsche Bank AG(NYSE: DB).
The U.S. benchmark West Texas Intermediate crude futures traded 0.05% lower at $58.06. Brent oil futures were up 0.03% at $64.22.