GOLDEN, Colo. -- A wind-driven wildfire burned 550 acres on Mount Galbraith northwest of Golden by Sunday evening, authorities said.

Sixty firefighters from five agencies are battling the wildfire in steep, rocky terrain that is not accessible to fire trucks, said Jacki Kelley, spokeswoman for the Jefferson County Sheriff's Office. A helicopter hoisting a 275-gallon bucket made 60 drops on the blaze burning between Clear Creek Canyon and Golden Gate Canyon.

Despite fire crews efforts, they had zero containment on the Indian Gulch Fire on Sunday night, authorities said.

The bigger worry is red flag-warning weather -- gusting winds and dry fuel -- forecast for Monday.

"It could be an explosive day," warned Golden Assistant Fire Chief Rocco Snart, the incident commander on the wildfire.

The early arrival of two big wildfires in March -- Indian Gulch and last week's Lefthand Canyon Fire in Boulder County -- has officials saying it could be a long, hot fire season for Colorado.

A lack of snow or rain on the Front Range has Snart saying this could be the worst fire season since 2002. That was the year the Hayman Fire, the largest wildfire in state history, scorched more than 138,000 acres, destroyed 133 homes, displaced 5,340 residents and wracked up $40 million in damages.

Shifting winds raised concerns about evacuations, but none were ordered Sunday, Kelley said. Golden police issued two automated telephone alerts on Sunday, advising 366 residents in the Mountain Ridge subdivision to be ready to evacuate if necessary.

Colorado's top state fire managers are on scene, Kelley said. If the fire worsens, federal firefighting resources could be mobilized.

The fire started at about 10:15 a.m. Sunday and was quickly spread by steady winds, Kelley said.

Fire crews were expected to continue fighting the wildfire until about midnight Sunday, then monitor the fire overnight.

Authorities closed U.S. Highway 6 on Sunday between Colorado Highways 119 and 93 while crews fought the fire. It's expected to remain closed at least into the Monday morning commute, said sheriff's spokesman Mark Techmeyer.

Firefighters from Golden Fire, Golden Gate Fire, Fairmount Fire, West Metro Fire and Wheat Ridge Fire were using hand crews to fight the wildfire.

The Red Cross said they had deployed a mobile feeding unit to provide refreshments for the more than 100 firefighters battling the blaze.