Billionaire Carlos Slim's Minera Frisco mining company increased its short position in the silver market in the first quarter to fund its development program, according to company filings.

Frisco, which reported earnings of $4.3 million in the quarter ended March 31, was short just under 95.759 million ounces of silver as of April 30 compared with a short position of 70.120 million ounces at the end of 2010, according to filings with the Mexican stock market. The company said the short positions were assumed to support the company's investment program.

In its most recent filing, Frisco reported a short position of a notional 34.478 million ounces in silver swaps at an average price of $25.06 per ounce as of April 30, according to filings with the Mexican stock market.

The company was short 24.840 million ounces at an average price of $18.82 an ounce as of Dec 31.

Frisco also held a notional 61.28 million ounces in options collars on silver with a long put positions at an average of $23.82 an ounce as of April 30, along with offsetting short call positions at an average of $39.97 an ounce.

As of the end of Dec 31, Frisco's silver options collars amounted to 45.280 million notional ounces with an average put price of $21.79 per ounce and an average call price of $39.70 per ounce.

The positions mature between 2011 and 2013.

Frisco's hedging positions are heavily out of the money even after silver's recent correction. Spot silver was bid at $39.36 an ounce in late trading on Wednesday.

Frisco reported a steep decline in quarterly profit on Monday due in part to margin calls on its short positions.