GRAND FORKS, N.D. (AP) - Manvel's fire chief says the director of the University of North Dakota's Energy and Environmental Research Center threatened firefighters who were attempting to put out a grass fire.

The North Dakota attorney general's office has been asked to investigate the last week's confrontation.

Manvel Fire Chief Steve Schumer said firefighters were dispatched at 8:45 p.m. on April 19 to a grass fire north of Grand Forks on property owned by Gerald Groenewold. A member of the Manvel firefighting crew lives near where the fire was burning and informed Schumer that the burn was controlled.

"Our protocol is that once we are dispatched, we don't leave until the fire is out," Schumer said. "We can't just turn around."

Once firefighters were on the scene, attempting to extinguish the fire, Groenewold became upset, Schumer said. One of Schumer's firefighters told him that Groenewold had threatened the crew saying, "if we aren't off his property in 10 minutes he was going to get a shotgun," Schumer said.

"At that point, (Groenewold) left for a moment and came back with something in his hands," Schumer said. "Because of the previous discourse, one of my guys yelled, 'He's got a gun,' and I immediately got my crew out of there and called the sheriff's office."

Schumer said that neither he nor any of his crew saw a firearm.

Grand Forks County sheriff's deputies were called to the scene, and restrained Groenewold. The 15-person fire crew was able to go back into the area and extinguish the fire, Schumer said.

Attempts to reach Groenewold on Tuesday were unsuccessful.

Grand Forks County's State's Attorney Peter Welte said Tuesday that his office forwarded the case to the Attorney General's office because of a perceived conflict of interest. Groenewold's wife is County Commissioner Connie Triplett. Triplett, a Democrat, also represents District 18 in the North Dakota Senate.

Welte says he is prohibited by law to discuss the facts of any ongoing investigation.

The Grand Forks County state's attorney has asked the state's Attorney General's office to investigate a confrontation last week between Energy and Environmental Research Center director Gerald Groenewold and Manvel, N.D., volunteer firefighters, officials said.