BRUSSELS, Aug 31 (Reuters) - A shipment of an unauthorised GMO rice strain from the United States arrived in the Netherlands on Saturday, the European Commission said.

"We do have a suspected positive case in Rotterdam," Commission spokesman Philip Tod told a news conference on Thursday, adding that the rice had not entered the market and was being tested by Dutch authorities.

"We also have been told by industry of another suspected positive case in New Orleans, but that has not left the U.S."

Last week, the EU tightened requirements on U.S. long-grain rice imports following the discovery by U.S. authorities of a genetically modified (GMO) strain known as LL Rice 601 marketed by Germany's Bayer AG and produced in the United States.