The Trump administration has launched an investigation into California’s high-speed rail project in what could be the first step in clawing back the $4 billion promised by the Biden administration to build out the first section of the line, from Merced to Bakersfield.

President Donald Trump canceled nearly $1 billion in federal funding for the high-speed rail project in 2019, during his first term. The Biden administration later restored the funding and, in December 2023, allocated $3.3 billion more.

The transportation secretary, Sean Duffy, said the government would conduct a “compliance review” on a $3.1 billion grant, potentially threatening the viability of the troubled project.