MIAMI (AP) — Three fatal crashes involving vehicles transporting migrant farmworkers have revealed the government is ineffective in enforcing agricultural transportation safety laws, federal investigators said Tuesday.

The National Transportation Safety Board issued findings and recommendations after a probe into a 2016 crash near St. Marks, Florida, that left four dead, and dozens more injured after a bus carrying migrant workers ran a stop sign and was struck by a tractor-trailer.

The 56-year-old driver of the farmworkers' bus was likely suffering from sleep deprivation, the board found. It...