Five Utahns were listed as "probable" with the swine flu virus on Thursday, the same day the LDS Church announced that new missionaries headed to Mexico will remain at Missionary Training Centers "until further notice."

Seeking to quell fears and assure the public of government readiness after word that four additional Utahns may have contracted the virus, Gov. Jon Huntsman Jr. told reporters Thursday that officials want Utahns "to be alert but not alarmed." The first "probable" Utah case was announced Wednesday.

The Church of Jesus Christ of Latter-day Saints announced in a short statement that new missionaries assigned to serve in Mexico will remain at the Missionary Training Centers in Utah and Mexico City "until further notice," and that it has "canceled all worship services in Mexico until further notice" upon recommendation of the Mexican government.

Mexico is home to more than 1 million Latter-day Saints and 20 LDS missions.

Thursday's midday press conference at the state Capitol was called after officials in Park City closed schools Thursday morning after lengthy discussion about the fact that three students there were among the "probable" cases and their samples had been sent to the Centers for Disease Control and Prevention for further testing.

"Please use common sense. We don't want hysteria to prevail," the governor said. "Everyone has lives to live, and we have a great economy in this state. We don't want a sense of overreaction."

Tom Hudachko, spokesman for the Utah Department of Health, said Utah has three "probable" cases of swine flu in Summit County, one in Salt Lake County and one in the Weber-Morgan area.

Test results are expected from the CDC, but there is no firm time estimate on when they will arrive.

Dr. David Sundwall, executive director of the Utah Department of Health, told reporters he believes school officials in Park City "erred on the side of being cautious, but I don't fault them for that decision." He said he would have preferred that the CDC not disclose the probable cases before they were confirmed, but because the federal health agency made the disclosure, Utah officials decided to announce it as well.

At this point, the virus doesn't seem to be any more serious for the vast majority of those who have it than a seasonal flu is, Sundwall said. The concern is that, because it is a new type of flu, there is no human immunity to it and no vaccine to prevent it from spreading.