UPDATE 2-Russia bans pork imports from 4 US plants -USDA

(Recasts, updates with USDA comment that ban may relate to antibiotic tetracycline)

CHICAGO, April 29 (Reuters) - Russia, a leading market for U.S. pork, has banned pork imports from four U.S. plants amid concerns about an antibiotic in the meat, the U.S. Agriculture Department said on Tuesday.

News that Russia banned pork from two Tyson Foods Inc. TSN.N plants and two Farmland Foods plants sent U.S. hog prices sharply lower at the Chicago Mercantile Exchange.

Russia claimed the antibiotic tetracycline was found in some of the pork, the USDA said on Tuesday after reporting the ban on its Web Site late on Monday.

“These things come up occasionally, even with Russia. They claim they have found tetracylcine showing up,” said USDA spokesman Keith Williams.

Williams said such things usually are resolved quickly, possible “in a matter of couple of weeks.”

The U.S. Meat Export Federation, plus meat companies Tyson Foods Inc. and Smithfield Foods Inc., said they were investigating Russia’s action. Farmland Foods is a unit of Smithfield Foods.

The affected plants include the Tyson’s facilities in Storm Lake, Iowa, and Logansport, Indiana; and the Farmland Foods’ plants in Crete, Nebraska, and Monmouth, Illinois.

“Initially it is a big blow considering the high hog slaughter that we have,” said John Kleist, broker/analyst with Allendale Inc. “Now the futures market seems to be awaiting some rationale of why they are doing it and is it science based or protectionism based.”

Through February, Russia was the No. 5 export market for U.S. pork this year, buying 26,716 metric tonnes, up 164 percent from a year earlier, according to the U.S. Meat Export Federation, a trade association that compiles USDA export figures.

Pork export figures from the USDA are delayed about two months and reports for March and April will still show very good exports of pork to Russia, said Bob Vande Vorde, livestock analyst with Mast Group LLC.

U.S. pork exports have been setting records for several years due to strong demand from growing economies overseas and ample supplies of U.S. pork. Also, lately the weak U.S. dollar has helped drive export sales, the USMEF said.

In midday trading. CME June hog futures were down 2.8 cents, or 3.71 percent, at 72.650 cents per lb.

Additional reporting by Jerry Biesk, Chicago, and Christopher Doering and Ayesha Rascoe in Washington; Editing by David Gregorio