Authorities are investigating a suspicious weekend house fire they say occurred while the homeowner, a single mother of three, was in Washington, D.C., for the presidential inauguration.

They also are trying to determine if she may have been targeted because of her support for President Barack Obama.

No one was home when the house on Lanier Drive in northeastern Forsyth County burned to the ground about 4:30 a.m. Sunday. Someone spray-painted graffiti that included a racial slur and the phrase "your black boy will die" on a fence along the property.

Forsyth County Fire Marshal Steve Anderson said the fire is considered "suspicious," but would not say it was racially motivated.

"What we're doing right now is we're investigating a suspicious house fire," he said. "There are indications that there may have been some type of terroristic threat.

"We cannot verify that at this time, not knowing how [the graffiti] got there, who it was for, several things. But right now we're just looking at it as a suspicious fire with suspicious circumstances."

Anderson said he spoke briefly on the phone with homeowner Pam Graf, who returned to Georgia from the nation's capital late Monday night. He planned to meet with her Tuesday.

Attempts to reach Graf for comment were not successful. But her father, William Morrow, said he thinks she was targeted because of her political views.

Morrow said Graf had two Obama campaign signs in her yard before the fire. He wasn't sure what happened to one sign, but said he asked her to remove the other after she received a negative letter about a week before the fire.

Morrow said the letter addressed her political views, though he couldn't remember any specifics from it that his daughter had shared with him.

He said she had taken the sign out of her yard before she left Friday.

Anderson said if fire investigators determine that the graffiti is a possible threat against Obama, they will involve the Secret Service. The department's Atlanta field office was closed Monday for the Martin Luther King Jr. holiday.

"Once I sit down and talk with her and we can discuss this a little bit more in depth, if we feel that's what it is, we'll call them and give them the information and see what they want to do," he said.

Anderson said the Forsyth County Sheriff's Office has been notified, but is not yet involved in the investigation.

"It's ongoing and we've got investigators out today working on it," Anderson said Monday, adding that the sheriff's office has offered to help.

"If we need it, we're going to take advantage of it," he said. "We're still very early in, we're still trying to collect information dealing with the fire. At this point in time, we can't even say the fire was an intentionally set fire, it's just suspicious."

Graf's three children, ages 11, 14 and 17, did not travel with her over the weekend, but stayed with family. Morrow said they were back at school Tuesday.

Morrow said Graf did not actively campaign for Obama in Forsyth County. A few years ago, however, she lived in Delaware and supported 2004 presidential candidate John Kerry.

He said Graf told him she attended a Democratic party meeting last week, but he was not sure of her involvement in the group.

Despite its strong Republican leanings, Forsyth County is home to many Obama supporters. The president received about 20.4 percent of the county's vote in the Nov. 4 presidential election.