(CNN) A ski resort in Colorado has had a Covid-19 outbreak, with over 100 active infections among its employees.
The Colorado Department of Public Health and Environment announced the outbreak at Winter Park Resort in January but released the data in its weekly outbreak summary on Wednesday.
There are at least 109 employees with active infections, they said.
"It has been determined that these cases have not been traced back to transmission through interaction with visitors but, rather, from social gatherings outside of the workplace and congregate housing," Grand County, Colorado, officials said Monday in a joint statement with Winter Park Resort.
With ski season in full swing in Colorado, other resorts have also reported Covid-19 cases. But the outbreak at Winter Park is currently the largest, according to CDPHE data.
"We have been working closely with public health authorities since the pandemic began," said Jen Miller, communications manager at the ski resort. "We did extensive planning and had to get approval from the state on our operations before we could open on December 3."
Most of the cases have been traced back to social gatherings outside of work and to congregate housing, Miller said.
Precautions, according to Miller, include: reconfiguring lift corrals and lift-loading procedures, extra staff, new signage reminding visitors about mask requirements, limitations on dining, a reservation system to manage visitation and the number of people at the resort, contactless lodging and a state-approved testing site for their 1,700 active employees.
But some visitors have reported that mask mandates were not being enforced.
When asked about those reports, Miller said, "We've done extensive work and continue to evolve our operations as necessary. I can't speak to one individual's experience, but we do appreciate feedback and will continue to make modifications with the health and well-being of our employees, guests and community as our top priority."
Conor Cahill, press secretary for Colorado Gov. Jared Polis, said ski resorts across the state need to "do a better job planning for and managing surge weekends."
Even though vaccinations continue to be rolled out, many US employees have risked Covid-19 by going to work.
In October, Amazon reported that nearly 20,000 employees became infected with the virus. And one study found that 20% of grocery store workers at a store in Boston had the virus.
Some corporations, like Aldi, Dollar General, Trader Joe's and Instacart, have started paying employees to get vaccinated in an effort to curb outbreaks.