Laurel Morales/KJZZ

One of the Navajo Generating Station's three 750-megawatt generators.

Two companies that had planned to take over the west's largest coal-fired power plant have ended their efforts to acquire it.

Salt River Project, the utility that operates the Navajo Generating Station, plans to shut down the plant in 2019 in favor of lower natural gas prices.

The plant's coal supplier launched a long-shot bid to find a buyer. New York-based Avenue Capital and Chicago-based Middle River Power showed initial interest, but ultimately said they could not overcome the challenges.

The Navajo and Hopi Tribes rely heavily on coal revenue. Navajo Speaker LoRenzo Bates said the tribe plans to pursue other viable buyers. But Salt River Project said it isn't actively working with anyone else.