BILLINGS (AP) — Lab tests have detected petroleum in of some of the fish taken from the Yellowstone River downstream from where a ruptured oil pipeline spilled an estimated 30,000 gallons near Glendive in January.

As a result, Montana Department of Fish, Wildlife and Parks has continued its fish consumption advisory for the stretch of river.

“We weren’t expecting to find it,” Trevor Selch, FWP’s pollution control biologist, said Friday.

The pipeline owned by Wyoming-based Bridger Pipeline LLC ruptured Jan. 17 where it crosses the Yellowstone River upstream from Glendive, dumping crude oil into the water.

Fisheries biologists were able to capture shovelnose sturgeon, sauger, channel catfish, goldeye, burbot and shorthead redhorse suckers below the spill.

“We’re lucky that we got a variety of species,” said Mike Backes, FWP fisheries manager in Miles City. “We also took the gills and livers of the fish to do histology. That’s where it goes to quickest if there’s any absorption.”

The fish were sent to laboratories in Billings and Wisconsin, which tested the edible muscle tissue as well as internal organs for polycyclic aromatic hydrocarbons.

Selch said results showed detectable levels of oil contaminates in some of the sauger, goldeye and shovelnose sturgeon. FWP is waiting for results from other tests.

Published research indicates that petroleum compounds can accumulate in fish for 40 or more days after a spill. Petroleum compounds can also be passed on to fish through the food chain when micro-organisms, insects, worms, crustaceans and other aquatic animals absorb petroleum compounds that are eaten by fish.

FWP will resume catching and testing fish after the ice leaves the river and test more fish tissue.

But Backes tells The Billings Gazette that the Yellowstone River’s native fish tend to begin moving upstream as spring runoff begins. That means it will be more difficult to say where the fish captured came from.

In addition, Backes said there will be “a tremendous dilution factor” by the time FWP crews sample again, since so much time has passed since the spill and with the added water from early spring snowmelt.