Oil traders are on edge over concerns that an emergency order from the U.S. Department of Transportation this week requiring shippers to test all crude before it is carried by train could cut into deliveries of Bakken crude. U.S. crude oil futures prices briefly spiked as much as 60 cents per barrel, or nearly 1 percent, earlier on Friday amid an apparent rumor that two terminals may have been shut down for non-compliance.

The U.S. Federal Railroad Administration said talk of shutdowns was "a rumor." A spokesman for the U.S. hazardous materials regulator said he was unaware of any shutdown.

However, data from industry intelligence group Genscape did show that loadings at a dozen major Bakken rail terminals had fallen to around 345,000 barrels per barrel on average for the past two days, down from about 550,000 bpd over the previous two weeks, an unusual but not unprecedented dip.

Genscape, which uses cameras to monitor the number of tank cars filled with crude at the terminals, provided no explanation for the dip. Analysts said the ebbing flows could also be due to other factors, including a shortage of oil tank cars and slower rail traffic due to severe winter weather.

Operators Enbridge Inc (>> Enbridge Inc) and Dakota Plains Holdings (>> Dakota Plains Holdings Inc) said their terminals were operating as normal. Other big operators including EOG Resources Inc (>> EOG Resources Inc) and Global Partners LP (>> Global Partners LP) did not immediately reply to requests for comment.

The Genscape data, made available to Reuters, showed that only 220,000 barrels were loaded at the terminals on Wednesday, the day after the DOT order, an exceptionally low rate.

On Thursday, seven of the 12 terminals monitored by Genscape loaded a total of 470,000 barrels; five terminals did not load at all, although two of those had been operating on Wednesday, according to the data.

(Reporting by Jonathan Leff, Jeanine Prezioso, Edward McAllister, Nia Williams and Timothy Gardner; Editing by Marguerita Choy)