Two major technology firm leaders have left Facebook founder Mark Zuckerberg’s political action group FWD.us in protest of the committee’s decision to fund advertisements supporting the controversial Keystone XL pipeline and drilling in the Arctic National Wildlife Refuge.

According to Think Progress, Elon Musk, CEO of Tesla Motors and Yammer founder David Sacks left the group, which claims that immigration reform is its major policy interest, over the millions of dollars it has spent promoting anti-environmental causes.

ADVERTISEMENT

Musk told the website AllThingsD in a written statement, ““I agreed to support Fwd.us because there is a genuine need to reform immigration. However, this should not be done at the expense of other important causes.”

Musk and Sacks were listed as “major contributors” on the FWD.us website, but as of Saturday, their names had been removed.

A coalition of liberal groups announced earlier this week that they were suspending all advertising on Facebook over support of the Keystone pipeline, which would carry natural gas and oil from Canada’s tar sands to refineries on the Gulf of Mexico.

Environmentalists and others worry that the multi-billion-dollar project will endanger fragile ecosystems and continue the country’s dependence on fossil fuels. A similar, much older pipeline recently ruptured under the town of Mayflower, Arkansas, creating a toxic mess that will take the region years to recover from.