Undated (AP) _ Sugar futures prices rocketed to new 1989 highs Thursday on rumors that Mexico, historically a net exporter of sugar, had purchased 400,000 tons of refined white sugar on world markets because of a domestic shortage.

The Mexican government later denied the rumors, which had triggered massive buying of sugar futures on both New York's Coffee, Sugar & Cocoa Exchange and the London Futures and Options Exchange.

On other markets, grain and soybean prices tumbled over concern that supply exceeded demand; livestock and meat were mixed; energy futures gained; and precious metals retreated.

New York sugar futures settled .39 cent to .49 cent higher with the contract for delivery in March at 10.97 cents a pound, it's highest settlement price since Dec. 30. March sugar traded as high as 11 cents a pound during the session.

Mexico had been rumored earlier in the week to have purchased 75,000 metric tons of sugar from the French trade house Sucres et Denrees. Even so, Thursday's reports of larger-scale buying took traders by surprise.

Arthur Stevenson, an analyst with Prudential-Bache Securities Inc. in New York, said the rumors incited heavy buying of sugar contracts by futures speculators.

Trading volume in New York soared to 40,000 contracts, compared with about 30,000 on Wednesday and 23,000 on Tuesday.

Analysts said Mexico may have overextended itself on export commitments and needed to replenish supplies for its own use.

Wheat led the late decline in grain and soybean futures on the Chicago Board of Trade, with much of the selling based on news that a sale of 1.5 million metric tons of French wheat to the Soviet Union was expected to proceed smoothly.

The report disappointed market participants who had recently bid up wheat prices on indications that some European grain producers were running into logistical problems in meeting their sale commitments to the Soviets.

Wheat settled 2 3/4 cents to 9 cents lower with March at $4.22 a bushel; corn was 3/4 cent to 2 3/4 cents lower with March at $2.69 a bushel; oats were 3 1/4 cents to 4 1/4 cents lower with March at $2.04 1/4 a bushel; soybeans were 3 1/2 cents to 11 1/4 cents lower with March at $7.27 1/4 a bushel.

Livestock and meat futures ended mixed on the Chicago Mercantile Exchange in cautious trading ahead of an Agriculture Department report on the number of cattle on feedlots in the seven largest cattle-producing states.

The report, issued after the close, showed 7.7 million head of cattle on feed as of Feb. 1, a 2 percent reduction from a year ago.

The report also showed a 5 percent decline in marketings of cattle off of feedlots last month and a 3 percent increase in the number of cattle placed on feedlots during January.

The USDA figures were all within the trade's expectations, so analysts said the report would have little impact on livestock futures prices on Friday.

Live cattle settled unchanged to .33 cent higher with April at 75.47 cents a pound; feeder cattle were .10 cent lower to .10 cent higher with March at 81.72 cents a pound; hogs were .12 cent lower to .08 cent higher with April at 41.97 cents a pound; frozen pork bellies were 1.40 cents lower to .58 cent higher with March at 37.90 cents a pound.

Energy futures finished higher in a day of seesaw trading on the New York Mercantile Exchange.

West Texas Intermediate crude oil settled 8 cents to 30 cents higher with March at $18.33 a barrel; heating oil was unchanged to .91 cent higher with March at 49.65 cents a gallon; unleaded gasoline was .24 cent to 1.10 cents higher with March at 49.05 cents a gallon.

Gold and silver futures slipped lower in dull trading on New York's Commodity Exchange.

Gold settled $1 to $1.10 lower with April at $387.10 a troy ounce; silver settled 1 cent to 1.1 cents lower with March at $5.895 a troy ounce.