Two Senate Democrats have demanded an investigation into the safety of oil transport in the United States after two derailments in the past two weeks.

Energy and Natural Resources Committee Chairman Ron Wyden (D-Ore.) and Commerce, Science, and Transportation Committee Chairman Jay Rockefeller (D-W.Va.) made the request to Transportation Secretary Anthony Foxx and Energy Secretary Ernest Moniz after a July derailment in Quebec that killed 47, a November derailment of an oil shipment in Alabama that caused explosions, last week’s North Dakota derailment that required 1,500 people near the fire be evacuated, and another Canadian derailment and fire this week near the Maine border.

The rail accidents could give ammunition to politicians wanting to decrease production of fossil fuels.

Given the growth of the Bakken oil fields in North Dakota, the senators wrote, “the federal government must have a thorough understanding of the risks to communities near active oil train routes, as well as the current and future volumes of oil being transported by rail.”

They asked the Government Accountability Office last year to examine “the impact of shale oil and gas development on transportation infrastructure and safety,” and are still awaiting the GAO’s findings.

Rockefeller and Wyden want an investigation begun to “thoroughly understand the current and future volumes of crude oil that will be shipped on railroads; evaluate the crudes to understand whether they require special precautions and handling; evaluate and update safety requirements to ensure they adequately address the risks of carrying crude oil; and finalize DOT’s rule implementing the rail risk reduction program that was signed into law in 2008.”

“The recent derailments and accidents involving crude oil are alarming and demand increased vigilance. We urge you to work together to quickly resolve issues with the transportation of crude oil in order to protect our communities, and prevent any further disasters,” the senators wrote.