Three cities in the United States and Graz, Austria, are considering joining Sapporo and three others in the bid to host the 2026 Winter Olympics, the International Olympic Committee said Tuesday.

On the first day of the IOC Session ahead of the Pyeongchang Games, Sapporo, Calgary, Stockholm and Sion, Switzerland, entered the dialogue or initial phase of the bid process, the IOC's Olympic Games Executive Director Christophe Dubi said.

Dubi said on top of those four cities, Denver, Reno-Tahoe and Salt Lake City from the United States, as well as Graz, have expressed interest. They have until the end of March to commit, and Dubi said the IOC will gladly lend a hand to any others that are thinking about running.

"We have this new process where we provide a lot of expertise up front and a number of technical visits with the four cities," Dubi said. "We have until the 31st of March for any interested cities to sign at the bottom of the page and work with us for the rest of the (dialogue phase)."

"So far we have seen interest from Austria and (United States). I'm certain that some of the delegations of the interested cities might join here. That's very pleasing to us."

"(We are) very confident with that process. We think we've done the right thing to make it lighter, more engaging, more collaborative."

Sapporo would be the third consecutive Asian city to host the Winter Games after Pyeongchang, which opens on Friday, and Beijing in 2022. The capital of Japan's northernmost main island previously hosted the 1972 Winter Olympics.

The IOC also said it is doing everything it can to contain a potential outbreak of the norovirus after 41 security guards suffered diarrhea and vomiting at a facility in Pyeongchang.

Around 1,200 security workers are being told to stay in their rooms as they are tested for the norovirus, according to the Pyeongchang Olympic organizing committee.

While food and water have been suspected as the source of the virus, Dubi said their standards have been upheld to the highest order.

"It starts with information," Dubi said. "Leaflets will be distributed to all populations about what to do."

"Very stringent measures are in place when it comes to food and beverage and the standards are to be respected. We don't know exactly what the source was, but when it comes to the food and beverage and the whole chain of securing the quality, they are respecting all international standards in this respect."