The two-story abstract mural — featuring a pharaoh's headpiece, a cotton field and fire spewing out of rowhouse windows — showed up suddenly this summer on a vacant house in North Baltimore.

The artwork at 4727 Old York Road came with a political twist: A sign next to it prominently listed the name of a trust that owns the house and those of government officials who represent the area.

The mural and sign are the work of a local group of artists who call themselves "Wall Hunters" and a housing activist seeking to publicly shame absentee landlords and elected officials into addressing the issue of vacant homes. The visual vigilantes have put up about a dozen murals across Baltimore this summer while risking trespassing and vandalism charges; their actions are done without the property owners' knowledge or consent.

"Most of these landlords are absentee," said the local artist known as "Nether," who helped found the Wall Hunters group. "They're destroying neighborhoods they don't live in."

But the project has drawn criticism from city officials and property owners. For at least two targeted properties, the people listed as property owners say they don't own the structures.

"We're extremely upset about it. I know we've contacted the police about it, and I know we're contacting multiple government agencies," said Danny Steger, who works for NB2 Business Trust, which owns the house on Old York Road.

City officials say the group is well intentioned but misguided, trying to assign blame for a complex problem rooted in economic realities and complicated by ownership tangles that have troubled the city for generations. Housing Commissioner Paul Graziano said "there are going to be situations where shaming the landlord isn't going to get you the outcome. I am not trying to shield these landlords from anything, but I am saying that's not an effective tool if there is absolutely no market there."

Vacant houses and other unoccupied properties are one of Baltimore's most visible and long-standing problems. The city has employed various methods — from selling houses for $1 to demolition — since Thomas D'Alesandro Jr. was mayor in the 1950s. Today, there are about 16,000 vacant, blighted properties within its borders.

Besides being eyesores, vacant houses drag down the values of nearby homes. They are magnets for fires and crime, and can collapse, causing injury or adjacent property damage.

Street artists have used vacant houses in Baltimore and in other cities such as Detroit as canvases for decades. But the overt political intention of the Wall Hunters is novel in Baltimore.

Housing activist Carol S. Ott, who since 2009 has used her blog, Baltimore Slumlord Watch, to highlight hundreds of run-down and neglected properties, launched the mural project with "Nether." (He initially declined to provide his real name, saying that was common practice for street artists, but the Wall Hunters website is registered to Justin Nethercut, a name the artist acknowledged was his.)

While Nethercut recruited artists for the project, Ott researched owners of the vacant properties, looking for housing or safety code violations, lawsuits, fines and histories of neglect. Alongside each mural, the group posted a QR, or quick response, code that leads to a post on the Baltimore Slumlord Watch blog with more information about the properties. The artists even incorporated Wall Hunters Inc., as a tax-exempt entity; Nethercut said it was funded by an anonymous donor.

Nethercut acknowledges that the murals are illegal, though he prefers to term them unsanctioned. But he said he and other members of the group have not had any problems with the police. "Sometimes the police watch my back, but that's about it," he said.

Police declined to comment specifically on the project, but in a statement said that "any attempt to improve our communities must be supported so long as that effort remains within the law."

The group also takes a risk in attaching names to homes, as ownership can change. That was the case at 918 North Arlington Ave., where the portrait of a former farrier at an Arabber stable was painted along a wall. The mural said the vacant home belonged to a corporation whose resident agent is Anthony J. De Laurentis, but property records show the house was sold in late June for $3,125.

"It's not owned by us," De Laurentis said. "It was sold."

Ott said that had she known about De Laurentis' intentions, she would have targeted another home. "Had that information been available, the mural wouldn't have gone on that property," she said.

At 4727 Old York Road, where the street artist "Gaia" commingled images of African-American and Jewish history on the side of the house, a nearby sign listed NB2 Business Trust as the owner. But it incorrectly labeled the trust "A Stanley Rochkind controlled entity," according to Steger and Brian Spern, an attorney who represents both NB2 and Rochkind.

Steger said Rochkind is not part of the trust and does not own the home. Rochkind at one time was forced to sign a consent decree with the state to mitigate lead paint in nearly 500 properties.

Steger believes combining Rochkind's name with the images of a cotton field and windows that appear firebombed plays up stereotypes of Jews as slumlords who oppress African-Americans. "It's not just the vandalism alone. We believe it's a hate crime as well," he said.