Fire erupted in a huge pile of tires at a recycling plant Tuesday, sending black smoke billowing for miles across southeastern Wisconsin (search) and shutting down roads as firefighters tried to contain the blaze.

About six acres of Watertown Tire Recycling Co.'s (search) estimated 1 million tires were in flames Tuesday night, a smoldering mound expected to take days to burn itself out.

"Several days is being optimistic," said Jennifer Warmke, emergency management deputy director for Dodge County.

No one was injured, but crews had to fight through acrid smoke as they used construction equipment to try to isolate the burning tires from unburned areas.

About 30 tanker trucks were hauling water from nearby Watertown to spray on the fire, and more than a dozen area fire departments were called in to help, Warmke said.

The plant sits just outside Watertown, a city of about 22,000 residents 35 miles west of Milwaukee.

Rob Thiboldeaux (search), a toxicologist with the state Division of Health, said air quality had not yet become a concern for Watertown. The surrounding area is mostly rural.

State officials offered to relocate about 20 to 50 people living within a half mile of the fire but no one had taken them up on the offer, he said.

Tom Madsen, 45, who has a farm near the tire recycling plant, said tires had been piled on all sides of facility, raising risks of a fire. The plant grinds tires into chips and processes them into materials for other uses, such as road-paving or fuel.

"It couldn't handle that amount of tires," said Madsen, who said he could see the smoke from Milwaukee.

Burning tires release pollutants into the air and can send toxic runoff into streams. In 1999, thousands of fish were killed by runoff from a 140-acre tire dump fire that burned for five days in northeastern Ohio. In 1995, a tire fire on four acres near Traverse City, Mich., burned for more than 20 days.