DENVER -- There have been no confirmed cases of Swine flu in Colorado as of Tuesday morning.

The Colorado Department of Health said it is looking at several "highly suspect cases" but it has no confirmation on any of them from the federal Center For Disease Control and Prevention.

The health department said the test results for two earlier suspected cases have already come back negative.

On Monday, state health officials said it could be just be a matter of time before swine flu cases are confirmed in Colorado.

Calonge said he couldn't estimate when swine flu will show up in Colorado but said the ailment is "literally only a plane flight away."

"I have to admit I fully expect to identify cases in the near future, given the presence of the virus in other states. We should proceed with our planning accordingly," said Dr. Ned Calonge, chief medical officer for the Colorado Department of Public Health.

That plan includes monitoring people for flu-like illnesses and respiratory illnesses at hospitals and to stock up on supplies in the case of a pandemic.

"We will be receiving 25 percent of Colorado's allotment of the strategic national stockpile, which will include masks, gloves and other protective equipment as well as other antiviral medications," Calonge said. "This is to pre-position these supplies. We are not planning distribution at this time. Currently there appears to be no commercial shortage of antiviral medication in the state so we anticipate we will have adequate supplies between the national stockpile and the personal healthcare system."

Calonge said the best way to prevent the spread of the swine flu is to reduce one's risk by washing hands and taking other personal precautions. Residents should also have a "shelter in place" plan with enough supplies such as food and water for a few days, he said.

The state is asking individuals with mild flu-like symptoms to stay at home -- regardless of travel history.

"Children and adolescents with fever should not go to school or day care. Adults with fever should not go to work until their symptoms resolve," Calonge said. "Those with respiratory complications or medical indications that could be worsened by the flu should contact their health care provider."

The state health department opened its emergency operations center and set up a phone line -- 877-462-2911 -- to answer questions.

"We're preparing and being as aggressive as we possibly can," said Chris Lindley, the state health department's director of emergency preparedness.

Federal officials have confirmed 64 cases of swine flu in the U.S., including 17 new cases in New York City, four more in Texas and three additional cases in California. That brings the total number of cases confirmed by federal officials to 45 in New York City, 10 in California, six in Texas, two in Kansas and one in Ohio.

State health officials in California have confirmed three other cases, and Indiana authorities have confirmed one.

More than 1,600 cases of swine flu have been reported in Mexico, and the suspected death toll has surpassed 150.

The U.S. stepped up checks of people entering the country by air, land and sea, but Denver International Airport officials said they were taking only normal precautions.

Mexico-bound travelers leaving Denver on Monday stocked up on surgical masks and hand sanitizer but said they wouldn't change their plans despite the travel advisory.

"A hundred people a day probably die in Mexico City in car wrecks," said Jeff Henderson, 39, who was headed to a friend's wedding in Mexico. "It's just playing the odds, really."

Megan Tschopp, 28, and Isabel Hedges, 25, both of Jackson, Wyo., were flying from Denver to Guatemala for a six-week Spanish course with a stopover in Mexico City. They picked up surgical masks on their way to the airport and then turned off their cell phones so they wouldn't get flooded with calls from worried relatives.

"I mean, there's nothing they can do," Tschopp said.

Transportation Security Administration workers at Denver International were allowed to wear gloves and masks but weren't required to, airport spokesman Jeff Green said.

Green said the airport had its normal contingent of paramedics on duty but no extra staff. If an incoming flight crew noticed passengers with symptoms, a paramedic would board the plane to check, but that's normal procedure, he said.

Travelers arriving in Denver from Mexico City shrugged off concerns and said they had faith the Mexican government is doing everything possible to prevent the spread of swine flu.

"There's no panic. People are doing the things they normally do without fear and just paying attention to the news," said Arturo Bermudez, 81, a Denver resident who returned to Colorado after visiting relatives in Mexico City. He stepped off the plane with a surgical mask wrapped around his neck.

Alberto Morales, a Mexico City resident on a weeklong business trip to Denver, said about half the people on the plane were wearing masks. He also said he wasn't worried about the swine flu because "we're informed about it, there's medicine, and there's a cure for the illness."

"I think our government is managing things well," he said.

Jason Gridley, 34, and his fiancee Amy Rafferty, 30, arrived back home in Denver on Monday after nine days in Cancun, Mexico. They said they began getting concerned the last few days of their trip and got more worried after hearing reports about swine flu cases in New York tied to students who went to Cancun on spring break.

Gridley said his paranoia increased further once he and Rafferty arrived at the Cancun airport for their return flight and saw people wearing masks.

"If anyone was coughing or sneezing, everybody was turning and looking -- at least I was," said Gridley, adding that he bought hand sanitizer and avoided eating airport food.

He said he didn't see any masks for sale but would have bought one if he did "because I'm so paranoid."

Rafferty said she and Gridley planned to stay away from their relatives in Denver for a couple of days as a precautionary measure.

Denver Public Schools reminded teachers and students to wash their hands and take other normal precautions but didn't plan any extra scrubbing.

The Mesa County School District in western Colorado said it planned no extra cleaning and that the county health department was handling advisories on prevention.

Jefferson County Public Schools, the state's largest district, said it was taking normal precautions but nothing extra.

Flu deaths are nothing new in the United States or elsewhere. The CDC estimated that about 36,000 people died of flu-related causes each year, on average, during the 1990s in the United States.