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ABU DHABI/CAIRO, Feb 15 (Reuters) - Egypt's agricultural quarantine authority has rejected four cargoes of U.S. soybean due to higher-than-permitted levels of a fungus called ambrosia, traders told Reuters on Monday.

"The four vessels are around 30,000 tonnes each and are all of U.S. origin, the problems all happened this month," one Cairo-based trader said.

"The official rejection letters are soon to be issued," another trader said.

The head of Egypt's quarantine authority was not immediately available for comment.

Egypt's agricultural quarantine authority rejected the cargoes, which were destined for private buyers, as it said they contained a higher than allowed ambrosia seed level, above 10 kernels per kilogram, traders said.

"This is very rare in soybeans to have rejections like this and I haven't seen it happen in this manner before," Hesham Soliman, President of Medstar for Trading, said.

Soliman said it was difficult to challenge the quarantine's findings on ambrosia fungus as that would involve taking joint samples and sending them for analysis abroad.

"Unless you take a sample and send it abroad for analysis, no one can know," he said.

"This comes at a time when Egypt really needs the soybean for vegetable oil and this is a large quantity that cannot be replaced in a short period of time," he added.

Another Cairo-based trader said that if the rejection is on the basis of ambrosia only the shipments should have been sieved and accepted.

The rejected soybean cargoes come as Egypt, the world's largest importer of wheat, edges closer to a wheat supply crisis after confusion over its allowed level of the ergot fungus in its wheat imports.

The crisis erupted after a 63,000 tonne French wheat shipment destined for state grain buyer GASC was rejected by Egypt for containing traces of ergot, a common grains fungus, despite it meeting the 0.05 percent threshold allowed by the authority's specifications.

The agricultural quarantine authority had insisted on a zero percent ergot policy despite its contradiction with GASC specifications.

(Reporting By Maha El Dahan, Eric Knecht and Michael Hogan; Editing by Alexander Smith) ((Maha.Dahan@thomsonreuters.com; + 9712 4082101; Reuters Messaging: maha.dahan.thomsonreuters.com@reuters.net))

Keywords: EGYPT SOYBEANS/