Efforts continued Saturday to clean up more than 1,000 barrels of oil that spilled from a ruptured pipeline in the US state of Arkansas, officials said.

The US Environmental Protection Agency has categorized the incident, which happened Friday afternoon near Starlight Road North in the Arkansas city of Mayflower, as a major spill, indicating a release of more than 250 barrels of oil, ExxonMobil, the owner of the pipeline, said in a statement.

The company confirmed the existence of "a few thousand" barrels worth of spilled oil in the area, but said it is "staging a response for more than 10,000 barrels to be conservative."

No one was injured, but about 22 homes in the affected were evacuated, Exxon said.

Numerous crews were working Saturday to clean up the spill and to prevent it from reaching nearby Lake Conway, officials said Saturday.

Approximately 4,500 barrels of oil and water have been recovered, Exxon said.

It would be a "number of days" before those evacuated were allowed to return to stay, said Faulkner County Judge Allen Dodson, according to the website Arkansasonline.com.

"That's an ongoing battle," Dodson said. "The rain hinders us in terms of our ability to work and in terms of the water flow," he said.

The clean-up involved remediation crews in the neighbourhood, more than 100 workers from ExxonMobil, and 15 large vacuum trucks, according to Dodson.

Exxon said in its statement that officials were conducting continuous air monitoring in the area.

"The air quality does not present a human health risk, with the exception of the high pooling areas, where clean-up crews are working with safety equipment," the statement said.

It's still unclear what caused the underground pipeline to burst, Dodson said.

"It's just really too early to speculate," Dodson said. "I think Exxon has said that it's too early for them to go and open up the dirt and look. That may take some time to determine."