SALT LAKE CITY (AP) – Members of the Navajo Nation are suing over the voting system in Utah’s San Juan County.

The county closed polling places in 2014 and moved to a mail-in ballot system.

The Navajo Nation Human Rights Commission and several tribal members sued the county last week in U.S. District Court in Utah. They say the change denies Navajos the same ability to participate in elections as white voters.

San Juan County clerk John David Nielson did not immediately respond to requests for comment Thursday.

According to the lawsuit, postal service on the Navajo Nation is unreliable and not all Navajos can read English. Navajos can vote in person in Monticello, but the lawsuit says the distance Navajos have to travel is more than twice as far as white residents.