U.S. regulations are not strong enough to ensure the safe transportation of crude oil by rail, the minority leader of the Senate Energy Committee said.

Sen. Maria Cantwell, D-Wash., took a committee hearing on U.S. crude oil export policy to grill industry leaders on crude oil transport by rail. An increase in U.S. oil production has outstripped pipeline capacity, forcing many in the industry to use railways as an alternate transit method.

"Oil production has increased faster than the infrastructure needed to transport it in the safest ways," she said. "And I want to be clear about this. We currently do not have the regulations on the books to safely transport this product."

Several recent derailments in the United States and Canada involved the transport of oil from the Bakken reserve area in North Dakota. Bakken was classified last year as more volatile than other forms of crude oil and Cantwell said she wanted to ensure any new policies for rail were "holistic" enough to address all safety concerns.

Cantwell's frustrations were similar to those expressed this week by the Transportation Safety Board of Canada. A train carrying crude oil through Ontario derailed last week. More than 40 people died in a similar accident in Quebec in 2013.

Charles Drevna, president of the American Fuel and Petrochemical Manufacturers association, testified that members have invested more than $4 billion in safer rail cars in recent years.

"As pipeline infrastructure continues to come online, some such as the North Dakota Pipeline Authority expect rail shipments from the Bakken to level off as pipelines and new small refineries are built," he said.

North Dakota Gov. Jack Dalrymple this week said three pipelines -- Sandpiper, Dakota Access and Upland -- should be in service by 2018 and provide 895,000 barrels per day in new capacity.

New tank car standards are expected from the U.S. Department of Transportation in May.