Crews have recovered about 1,805 barrels (bbl) of oil from a creek in North Dakota following a Dec. 5 spill that leaked 4,200 bbl, making it the sixth-largest pipeline leak in 2016, according to government data.

The cause of the spill is still not known, said Wendy Owen, spokeswoman for True Companies, which owns the Belle Fourche Pipeline that leaked. Of the total spill, about 3,100 bbl leaked into the nearby Ash Coulee Creek, a small waterway that feeds the Little Missouri River, a tributary of the Missouri River.

The spill has been contained. During the week of Dec. 12, Owen noted that pipeline equipment did not detect the spill, possibly because the 2,400 bbl/d line runs intermittently.

The leak occurred just 150 miles from the site of protests against the Dakota Access Pipeline (DAPL), a crude line whose planned route was under the Missouri River. The Little Missouri feeds the main river upstream of the DAPL crossing.

The spill happened as pipeline companies such as Energy Transfer Partners LP, which saw DAPL halted in December by the U.S. government, are trying to convince critics that their systems are the safest way to move crude and other products.

The spill incident underscores concerns of the Standing Rock Sioux Tribe, whose land is adjacent to the planned DAPL route, and others who have said that a leak from DAPL could contaminate drinking water and desecrate sacred lands.

So far, the total number of hazardous liquids pipeline spills in 2016 is on track to fall short of 2015. As of Nov. 30, there were 354 spills, vs. 462 for all of in 2015, according to data from the Pipeline and Hazardous Materials Safety Administration (PHMSA).

However, the percentage of spills releasing larger volumes of liquids has been higher this year, the data shows.

About 16% of pipeline releases in 2016 involved 100 bbl or more of product, vs. about 13% in 2015. The percentage involving 1 Mbbl or more has been slightly higher as well for 2016 at 3.4%, vs. 3% in 2015.

The two largest leaks in 2016 have involved crude pipelines. In September, Sunoco Logistics, the operator of DAPL, spilled 8,600 bbl of oil from its Permian Express II Pipeline near Sweetwater, Texas. The company had previously been fined for violating welding practices on that line.

In October, Enterprise Products Partners' Seaway Crude Pipeline released more than 7,600 bbl of oil near Cushing, Okla.

Belle Fourche reported a 1,958 bbl leak of refined products on its system in Campbell County, Wyo., in 2011, and less than a month later suffered a 1 Mbbl spill of crude oil on its line near McKenzie, N.D.