A powerful Congressional committee has launched an investigation into the U.S. Environmental Protection Agency's denial of California's request to impose limits on greenhouse gas emissions from motor vehicles and other tailpipe toxics. It is the first time a waiver request has been denied under the federal Clean Air Act.

The Committee on Oversight and Government Reform has ordered EPA Administrator Stephen Johnson to preserve all documents relating to the decision he issued Wednesday not to grant a waiver of less stringent federal rules so that California's clean car law could take effect.

Committee chair Congressman Henry Waxman of California has requested that Johnson provide all the documents from his office relating to the California waiver request to the committee by January 10, 2008. Documents from all EPA offices relating to this decision are to be handed over to the commettee by January 23.

Announcing the denial, EPA administrator Johnson said the energy bill signed into law by the president earlier this week would be sufficient to curb greenhouse gases from cars because it mandates a 35 mile per gallon fuel efficiency standard for cars and light trucks across the country by 2020.