Sens. John Rockefeller (D-W.Va.) and Ron Wyden (D-Ore.) are pressuring administration officials to act quickly on railway transports of crude oil in the wake of multiple explosive derailments.
It's the second call for action by lawmakers, after North Dakota's senators met with officials on Thursday.
The letter also calls for the agencies to evaluate and update safety requirements.
"The recent derailments and accidents involving crude oil are alarming and demand increased vigilance," the senators wrote on Thursday. "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."