Updated from 10:03 a.m. EDTPork producers are assuring consumers their products are safe as the swine flu epidemic reached a public health emergency this weekend. But investors are weary. Shares of Smithfield Foods ( SFD) fell 13% to $9.00 in afternoon trading, while Tyson Foods declined 9% to $9.98. Smithfield said on Sunday that it found no signs or symptoms of swine flu in its herd or employees at its joint ventures in Mexico. The company said operations are cooperating with Mexican officials to assist it in its investigation of the possible sources of the outbreak of the disease and will submit samples from its swine herds to The University of Mexico for testing. The National Pork Producers Council said that according to the Centers for Disease Control and Prevention the U.S. Department of Homeland Security, "people cannot get the hybrid influenza from eating pork or pork products" and "preliminary investigations have determined that none of the people infected with the hybrid flu had contact with hogs." But fears about the disease are still expected to send the U.S. market lower today. Russia has already banned imports of meat products from Mexico, California, Texas and Kansas, and South Korea has said it will increase the number of its influenza virus checks on pork products from Mexico and the U.S.