( CNN ) -- Dozens more workers Monday joined the effort to clean up an oil spill that dumped hundreds of barrels of crude into Montana 's Yellowstone River over the weekend , ExxonMobil said . ExxonMobil said between 750 to 1,000 barrels ( 32,000 to 42,000 gallons ) of oil escaped late Friday when a pipeline ruptured beneath the river near Billings . Some of the oil has washed ashore or formed pools of `` milky brown '' residue in river eddies , Yellowstone County Sheriff Mike Linder said . High water and a swift current has helped break up the spill , local officials said . But cleanup efforts have been hampered by flooding that has made it harder to track and clean up the oil , said Linder and Duane Winslow , the county 's emergency services director . The Yellowstone was running above flood stage over the weekend , sweeping brush and logs into the river , and had a 5- to 7-mph current Sunday . `` It 's too dangerous to do anything on the river , to put out any sort of boats or anything , '' Winslow said . `` So people will be working from the shores rather than out in the middle of the river . '' About 80 people were expected Monday to join the 120 working to contain the oil spill , ExxonMobil said in a statement posted late Sunday on its website . Cleanup crews are using absorbent pads to soak up oil , boom to isolate oil that has pooled adjacent to the river and vacuum trucks and tankers to pick up and dispose of the oil , it said . The spill was discovered late Friday night near Laurel , west of Billings and about 100 miles downstream from Yellowstone National Park . The pipeline feeds an ExxonMobil refinery in Billings , and the company said it had shut down the line within minutes . `` We will stay with the cleanup until it is complete , and we sincerely apologize to the people of Montana for any inconvenience the incident is creating , '' Gary Pruessing , the president of ExxonMobil 's pipeline subsidiary , said in a statement issued Sunday . There were no reports of wildlife being endangered by the spill , Tim Thennis , who is leading the response for the Montana 's Disaster Emergency Services agency , said Sunday . Rescue worker with the International Bird Rescue also were expected to join cleanup efforts Monday , ExxonMobil said . The Montana Audubon Conservation Education Center and Yellowstone Valley Audubon have offered to provide wildlife recovery services and facilities , it said . The spill forced the evacuation of more than 200 nearby residents after it was discovered Friday night , but they were allowed to return Saturday morning . Laurel rancher Lloyd Webber said the spill left a `` pretty heavy '' smell of oil hanging over the area Friday night as he and his wife left their home . `` We went to the Perkins in Billings and drank coffee for two or three hours , then went back , '' said Webber , who lives about a half-mile from the river . ExxonMobil said it had received more than 70 calls to its community claims line . ExxonMobil did not say whether these calls were individual claims or what the claims were being made . The Yellowstone is one of the tributaries of the Missouri River , which it joins in neighboring North Dakota . Thennis said state agencies , the federal Environmental Protection Agency and ExxonMobil are working together to clean up the spill . CNN 's Matt Smith , Joe Sutton and Chelsea J. Carter contributed to this report .
High water and a swift current has helped break up an oil spill . Exxon says about 750 to 1,000 barrels of oil spilled in the Yellowstone . The spill occurred when a pipeline ruptured near Billings . Score: 6