 -- A Colorado wildfire that forced hundreds out of their homes on Sunday has been 50 percent contained, authorities said.

The fire near Sunshine Canyon in Boulder, Colorado -- just west of the downtown area -- scorched about 63 acres of land and forced the evacuation of 426 homes as authorities worried that erratic winds could cause the fire to spread further, the Boulder Office of Emergency Management said Sunday.

As a precaution, another 836 homes were placed on a pre-evacuation list amid worries that the blaze could flare up due to strong wind gusts overnight, emergency officials said.

There were no known injuries or homes lost as of early Monday morning, the Boulder Office of Emergency Management said.

Boulder County Sheriff's Cmdr. Mike Wagner said the area has "a very social trail network," leading authorities to speculate the fire could be “human-caused.”

"At this point, we’ve been able to rule out things like lightning strikes or weather related, downed power lines, things like that. That causes us to speculate that it’s human caused, manmade," Wagner said during a press briefing on Sunday. "In the general area where that fire was reported to us by Sunshine Canyon and Timber Lane is a very social trail network. A lot of people are in and out of there."

The fire began before early Sunday morning near Sunshine Canyon and Timberlane, emergency officials said.

Wagner said fire officials would remain at the scene overnight to attack hot spots and possible flare-ups.

He said people in the pre-evacuation zones should be prepared and ready to go at any time as the fire’s status could change due to windy weather overnight.

"The plan is to keep the mandatory evacuation zone in place," Wagner said in a video posted on the Boulder Office of Emergency Management’s Facebook page late Sunday.

"The forecasts is a little concerning. There’s a potential wind event at around midnight. It is very volatile there and there’s a lot of complicating factors that go into a fire operation overnight," he said.

The Boulder Regional Communications Center said it received a call from a man at around 2 a.m local time who said he noticed flames on the side of a mountain, according to the Boulder County Sheriff’s office.

Multiple fire departments, including the Boulder Rural Fire Protection District, the Boulder Fire Department, and the Sheriff's Fire Management Program, fought to contain the fire.

Officials said a shelter at the East Boulder Community Center would remain open overnight in case of additional evacuations.

Mark Sandercott, who was forced to evacuate, told ABC News affiliate KMGH that he feared of losing his home.

"I thought, for sure, we were probably going to lose the house," he said. "I grabbed my backpack, grabbed the most essential things that I thought I needed, and some water and just left."

The blaze is currently moving south, according to KMGH.

ABC News' Marilyn Heck, Matthew Fuhrman and Carol McKinley contributed to this report.