Gov. Brian Schweitzer also will join state disaster response and environmental officials for a media briefing on the spill at noon ET, according to his office.
The crisis began late Friday, when ExxonMobil reported that 750 to 1,000 barrels (32,000 to 42,000 gallons) of oil escaped through a crack in one of its pipelines in the Yellowstone River in Laurel, about 16 miles southwest of Billings. The company said it shut down the line within minutes, but not before toxins had been dumped in the water.
ExxonMobil said Monday night that more than 280 people have converged on the area near Billings, including workers from the Texas-based oil company and the Clean Harbors environmental firm. Schweitzer told CNN the cleanup effort has been "pretty good" thus far, though he criticized the speed and comprehensiveness of the response.
"Not all the assets that we wanted are here, and we're going to find out why," he said.
Lloyd Webber, a Laurel rancher, said the spill left a "pretty heavy" smell of oil hanging over the area.
Schweitzer noted that roughly one year ago, several state, county and local agencies held a "mock pipeline spill" drill on the Yellowstone River. Many of those organizations, including the Montana Fish, Wildlife and Parks Department, the state Environmental Quality Department and various Yellowstone County officials, are involved in the current effort in the southern part of the state.
Historically high water levels and rapid currents have made things difficult for those trying to clean up the spill. On Saturday, levels near Billings reached their peak for the season at 13.95 feet, nearly a foot above flood stage, according to the U.S. Geological Survey.
While the water conditions helped break up and dilute the oil spill, they also left cleanup workers with fewer options. Duane Winslow, Yellowstone County's emergency services director, said Sunday that crews have been forced to work from onshore for fear of being swept up in the water.
"It's too dangerous to do anything on the river, to put out any sort of boats or anything," Winslow said.
ExxonMobil said late Monday that many areas remained unsafe, adding that it has eight boats ready to go should conditions improve.
In terms of evacuations, flooding has -- and continues to -- affect more people in the region, thanks largely to the residual effects from the melting of massive winter snowpacks. About 200 residents were ordered out Friday night, and then allowed back in the next morning. That's significantly less than the hundreds who have been forced from their homes because of the persistent, far-reaching flooding in the area.
"We haven't seen a lot of issues around here (due to the spill)," said Nathan Hammond, who works at the Yellowstone River Campgrounds in Billings. "But there has been a lot of flooding, that has been a big issue."
Still, ExxonMobil reported in a statement that it had received 94 calls to its community claims line as of Monday night -- 36 of those coming from landowners reporting oil had washed up on their property.