BILLINGS, Mont. — Adventure seekers encounter untamed wilderness when they enter the backcountry of Yellowstone National Park. Howling wolves. Deadly grizzly bears. Steam-spewing geysers as seen nowhere else on earth.

A refuge from ringing cellphones? Not so much anymore. In the popularity contest between Yellowstone's natural wonders and on-demand phone service, park administrators appear to have lost ground on a 2009 pledge to minimize cellphone access in backcountry areas.

Signal coverage maps for two of Yellowstone's five cellphone towers show calls can now be received in large swaths of Yellowstone's interior.

The maps were obtained by a Washington, D.C.-based advocacy group, Public Employees for Environmental Responsibility, which has for years fought against new telecommunications infrastructure in the first U.S. national park.

Their release comes after lawmakers in the U.S. House recently introduced a bill that would allow even more cellphone towers and similar structures on public lands across the nation.

Yellowstone technology chief Bret De Young acknowledged the occurrence of “spillover” cellphone signals into backcountry areas but suggested the coverage maps — released by the park to PEER under a public records request — exaggerated the quality of coverage in parts of the park.

In 2009, Yellowstone issued a wireless and telecommunications management plan that said cellphone coverage “would not be promoted or available along park roads outside developed areas, or promoted or available in any of the backcountry.”

“No cellphone service will be allowed in the vast majority of Yellowstone,” park officials said in a statement issued when the plan was adopted.

PEER Executive Director Jeff Ruch said the park had failed to meet those goals and instead ceded its program to companies that wanted to offer blanket coverage.

“The ability to disconnect, the serenity value of that, is a park resource that they've given away without a thought,” Ruch said.

De Young said it is not the intent to cover backcountry areas, and the park is taking steps to limit cell service as much as possible to developed areas.

That's being done with the installation of new antennas that direct signals more precisely so cellphone services are limited mainly to the small communities and campgrounds in the park. Two of the park's five cellphone towers now use those specially aimed antennas, and De Young said a third is due to be converted this fall.

A cellphone coverage map provided by the park shows that the signals extend beyond targeted areas but lose signal strength as the distance from the communities and campgrounds increases.

The House legislation introduced last month, the Public Lands Telecommunications Act, seeks to encourage even greater cellular and broadband coverage within national parks and other public lands.

It would set up an account using rental fees for telecommunications companies with cell towers or other infrastructure on public lands. Money raised would be used by the U.S. Interior and Agriculture departments to obtain additional communication sites and take other steps to foster greater coverage.