KILLDEER -- A Dunn County roustabout service is estimating that $80,000 worth of crude oil was stolen from tanks it maintains at two well sites north of Dunn Center.

Greg Krueger, the owner of K&R Roustabout, said he reported the theft of about 760 barrels of oil to the Dunn County Sheriff's Office on July 1.

"Somebody is going in there and taking oil," Krueger said.

Cornerstone Natural Resources owns the wells, but Krueger said a K&R pumper was the first to raise a red flag after the amount of oil calculated in tanks at two different sites came up short and didn't match truck tickets.

Under North Dakota law, the theft would be considered a Class B felony, punishable by up to 10 years in prison, a fine of $10,000, or both.

Krueger said throughout the past two weeks, he has been "disheartened" by the effort being put into the investigation by the Dunn County Sheriff's Office. He said no one responded to his initial report until July 4.

"It bummed me out that the guys aren't taking it serious," Krueger said.

Dunn County Sheriff Clay Coker said his office is investigating the alleged theft, adding theft is the most probable answer to the missing oil because a seal to one tank was missing and a seal at another was broken. The sheriff's office is unsure of the exact dates the thefts occurred, but they are believed to have occurred over a weekend, Coker said.

Krueger said he thinks the thefts happened at night, adding that the well sites where the tanks are located are in secluded, rough terrain areas near the Little Missouri State Park.

K&R has set up motion-activated cameras typically used for monitoring wildlife at well sites, Krueger said, to help prevent further losses.

"We just hope to hell they come back and we catch them on the game cam," Krueger said. "I'd like to catch them. They're going to go to jail for a long time."

North Dakota Department of Mineral Resources spokeswoman Alison Ritter said her office's production audit department is aware of missing oil and is doing their part to help the investigation.

"Like anything else, it's a valuable property," Ritter said. "But the big thing where we would come in is if we could look at other run tickets we receive, and if anything seems off where we could provide a lead, we could do that."