Independent researchers reported detecting elevated methane levels as far as 8 miles from the massive, ongoing leak of natural gas from a storage site in northwestern Los Angeles. A ruptured well at Southern California Gas Co.'s Aliso Canyon underground facility has spewed more than 80,000 metric tons of methane into the atmosphere since the leak was discovered Oct. 23. The release of the powerful greenhouse gas led to the evacuation of thousands of people from the affluent Porter Ranch neighborhood a mile from the leak after reports by residents of nosebleeds, rashes, headaches and nausea.Finding elevated methane levels well beyond the Porter Ranch area raises potential health concerns for people living outside the immediate vicinity of the leak, the researchers said. Inhaling low concentrations of methane, the primary component of natural gas, is generally not considered a health concern, but natural gas often contains trace amounts of other, more harmful gases. "Whatever else may be in the gas-benzene, toluene, xylene -- that is what people may be breathing," said Nathan Phillips, an earth and environment professor at Boston University. "Even though we're not measuring things other than methane, there is a legitimate concern that there is that other nasty stuff in there." The findings challenge assurances from the South Coast Air Quality Management District, the regional air pollution control agency, and the state's Office of Environmental Health Hazard Assessment that the leak hasn't increased residents' exposure to toxic gases. The cumulative methane emissions from the Aliso Canyon facility to date have the greenhouse gas equivalent on the Earth's atmosphere of burning nearly 800 million gallons of gasoline, according to the Environmental Defense Fund. On Wednesday, Los Angeles City Councilman Mitchell Englander called on SoCal Gas to extend its residential relocation program to residents of neighborhoods adjacent to Porter Ranch, according to the Los Angeles Daily News. People in these communities were also reporting similar symptoms related to the leaking gas, according to the paper. SoCal Gas spokeswoman Kristine Lloyd said the gas company is providing temporary accommodation and air filtration for residents within a five-mile radius of the leak, extending beyond Porter Ranch. Democratic US Senators Barbara Boxer and Dianne Feinstein of California sent a letter to the Department of Transportation, the Environmental Protection Agency and the Department of Justice Wednesday calling on the federal agencies to offer further assistance to the State of California in responding to the gas leak. In a mapping effort funded by the Home Energy Efficiency Team, a Cambridge, Mass., nonprofit, Phillips and Robert Ackley of Gas Safety Inc. measured methane emissions for the past several days near the Aliso Canyon leak. Gas Safety Inc. provides natural gas leak detection services to industry, businesses and homeowners. They used a laser-based system mounted to a car. It recorded methane concentrations and plotted the readings on Google Earth. On Tuesday and Wednesday the researchers drove further from the leak and recorded methane concentrations as much as two times higher than background levels, as far as 8 miles away from the site.