* S.Korea to continue thorough LMO tests for imported products
* Vessel carrying Argentine feed wheat heading to Australia
* S.Korean feed wheat buyers looking into situation (Adds shipper, loading port details)
By Jane Chung
SEOUL, July 26 (Reuters) - South Korea rejected a shipment of Argentine feed wheat after finding unapproved strains of genetically modified organisms (GMO) in the cargo, the agriculture ministry said on Tuesday.
Seoul bans the entry of unapproved GMOs, defined as living modified organisms (LMO) under bio safety regulations.
In 2013, South Korean millers suspended imports of U.S. wheat after the discovery of an unapproved strain of genetically modified wheat in the United States.
"After testing 72,450 tonnes of feed wheat cargoes imported from Argentina on July 12, an unapproved strain of LMO was detected and we asked to discard or send all back," the ministry said in a statement.
The cargo was shipped by the bulk carrier ANTONIS, said an official at the Korean Animal and Plant Quarantine Agency.
The cargo was loaded at Argentina's San Lorenzo and Bahia Blanca ports in May and shipped by Netherlands-based commodity trader Nidera, according to data from NABSA shipping agency.
Nidera could not be reached immediately for comment.
Thomson Reuters ship tracking data showed the vessel is heading to Australia's Gladstone port after discharging at South Korea's Pyeongtaek and Kunsan ports.
The ministry said it would continue with LMO tests of imported agricultural products.
In Buenos Aires, a grains export company executive said there is no GMO wheat cultivated in Argentina.
"So it must have been something left in the hold of the ship from a previous cargo," said the executive, who asked not to be identified.
South Korea is not banning imports of feed wheat from Argentina, only the shipment containing the unapproved strain, a ministry official, who declined to be identified, told Reuters.
Feed importer Nonghyup Feed Inc said it is looking into the situation after the government's decision, while the Korea Feed Association could not be reached for comment.
Korea, Asia's fourth-largest economy, mostly imports feed wheat from Australia, India, Ukraine and Canada. It imported 396,900 tonnes of Argentine feed wheat in June out of total imports of 910,946 tonnes, according to the statement.
Ample Argentine wheat supplies and the low grain quality have pressured prices and boosted feed wheat shipments to Asia. Argentine farmers liquidated their wheat stockpiles after free-market proponent Mauricio Macri won the presidency last November and eliminated grain export taxes.
"When you analyse the destinations that Argentine feed wheat is being shipped to, there has been a radical shift toward Asia," said Leandro Pierbattisti, chief analyst with Argentina's grains warehousing chamber.
Reporting by Jane Chung; Additional reporting by Hugh Bronstein in Buenos Aires, Karl Plume in Chicago; Editing by Christian Schmollinger and Leslie Adler