BILLINGS, Mont. (AP) — Yellowstone National Park is in the midst of hiring up to 400 summer employees to staff up before tourists flock to the park.

Spokeswoman Linda Veress says seasonal workers can only be employed for six months. She says the park has to consider staffing needs during the park's busiest months when setting new hires' start dates.

The Billings Gazette reports that Yellowstone receives its highest number of visitors from June through September, but numbers typically peak in July.

More than 4.1 million people visited the park last year. Some local officials worried that the Department of Interior's proposal to increase park entrance fees would lower visits, but recent media reports suggest that proposal could be on hold.

Yellowstone spokeswoman Veress says most temporary employees must undergo a background check.