The Obama administration considered national standards to control explosive gas in oil trains last year but rejected the move, deciding instead to leave new rules to North Dakota, where much of the fuel originates, according to Reuters.

Current and former administration officials told Reuters that they were unsure if they had the power to force the energy industry to drain volatile gas from crude oil originating in North Dakota’s fields. Instead, they opted to back North Dakota’s effort to remove the cocktail of explosive gas — known in the industry as “light ends” — and rely on the state to contain the risk. North Dakota’s regulations come into force next month.

The administration’s internal debate shows that concern about the risks associated with oil trains reached the upper level of the White House. But the administration balked at addressing the problem in new regulations governing crude oil trains that it is preparing to introduce this spring, according to Reuters.

When Transportation Department and White House officials convened on this issue last summer, the administration decided to back North Dakota’s plan to limit vapor pressure — a measure that was just taking shape at the time.

But a growing number of safety advocates say relying on North Dakota is not sufficient to regulate a product that is hauled thousands of miles of track and across many state lines.