Hundreds of homes have been lost to massive and unprecedented Oregon wildfires with a potentially historic number of fatalities feared in the northwestern US state, governor Kate Brown said Wednesday. Intense and "unprecedented" wildfires have spread across Washington state, Oregon and California More than 300,000 acres are burning across Oregon including 35 major wildfires, with at least five towns "substantially destroyed" and mass evacuations taking place. "This could be the greatest loss of human lives and property due to wildfire in our state's history," Brown told a press conference. Along with neighboring California and Washington states, Oregon has been scrambling to contain rapidly spreading wildfires since the weekend due to unprecedented heatwaves followed by intense, dry winds. "I want to be upfront in saying that we expect to see a great deal of loss, both in structures and in human lives," said Brown. Early reports said towns and cities including Detroit, Blue River, Vida, Phoenix and Talent had been "substantially destroyed," she added. "Hundreds of homes have been lost. And we continue to carry out mass evacuations across the entire state." Weather conditions had not improved Wednesday, threatening more towns and cities and helping to ignite new fires. Dry vegetation has increased the risk of further "unprecedented" spread, with "significant damage and devastating consequences across the entire state" already suffered in the past 24 hours. Brown said she had enacted an emergency fire act for the entire state, granting immediate powers and resources to fire officials, and requested federal assistance. Neighboring California has already seen 2.5 million acres burn -- an annual record, with almost four months of the year remaining -- and at least eight deaths reported.