New numbers in a federal database show that a Dec. 30 train derailment near Casselton, N.D., spilled nearly 475,000 gallons of crude oil, more than officials originally estimated.

The Pipeline and Hazardous Materials Safety Administration maintains a database on such spills going back to 1975. A McClatchy analysis of the data last month showed that more crude oil was spilled from trains in 2013 than in the previous four decades combined.

The National Transportation Safety Board is investigating the accident, in which a derailed grain train caused the derailment of a crude oil train traveling the opposite direction on an adjacent track. The spilled oil ignited a massive fire, causing hundreds of nearby residents to evacuate.

No one was injured or killed, but he accident added to the anxiety of state and local officials about the safety of shipping large volumes of crude oil in minimally protected tank cars.

In July, 47 people were killed in Lac-Megantic, Quebec, when a similar train broke loose and rolled unattended down a steep grade and derailed. The explosions that followed leveled the center of the lakeside community.

Initially, the NTSB estimated that 400,000 gallons of crude had spilled in Casselton.

The new total means that more than 1.2 million gallons of crude oil spilled from railcars last year, not including the Quebec disaster. Only 800,000 gallons were spilled from 1975 to 2012.

Federal regulators are in the process of developing new standards for shipping crude oil by rail amid concerns about its flammability. Crude from North Dakota’s Bakken shale region has drawn special scrutiny because of its involvement in multiple fiery derailments.

The Senate Commerce Committee has scheduled a Thursday hearing on the matter, and the House Transportation Committee will hold its own hearing later this month.