(Adds fire widens, more homes threatened, pre-evacuation orders, other details, in paragraphs 1-5)
By David Schwartz
PHOENIX, May 21 (Reuters) - A major wind-whipped fire burned through a popular scenic canyon in Arizona on Wednesday, ballooning to 4,500 acres (1,800 hectares) and threatening about 300 residences and businesses, fire officials said.
About 500 firefighters were battling the so-called Slide Fire late on Wednesday afternoon and more than 3,000 residents from two subdivisions were put on alert for possible evacuation near Oak Creek Canyon, about 120 miles (200 km) north of Phoenix.
An undetermined number of residents along a 2-mile (4-km)stretch near the canyon had already been evacuated, officials said. They said the blaze was burning about 3 to 4 miles (5 to 6 km) from the nearest residence.
"The fire has really been active and very aggressive," said Brady Smith, a Coconino Forest Service spokesman. "We really have a big job on our hands."
Smith said sustained winds with gusts of up to 35 miles per hour (56 km per hour) caused the blaze to roar. The fire, which has been creeping up steep canyon walls and at one point eclipsed the canyon rim, is at zero percent containment.
Crews are stationed above and below the fire, which has been moving to the north. Additional personnel were expected to arrive, including an elite Type 1 incident management team that was to deploy on Wednesday night.
The fire, believed to be human-caused, broke out at about 4 p.m. on Tuesday north of Slide Rock State Park, a popular recreation area.
The American Red Cross has set up an emergency shelter at a middle school in nearby Flagstaff, Arizona, for those forced to flee their homes. (Reporting by David Schwartz in Phoenix; Editing by Dan Whitcomb, James Dalgleish, Cynthia Johnston and Mohammad Zargham)