SAN FRANCISCO -- A mysterious, greasy goo of unknown origin is seeping into garages and basements near San Francisco's Balboa Park. Residents suspect a nearby Muni yard may be the source, but so far the city has helped little in attempts to determine what the substance is and where it's coming from.

For a half century, Josephine Paras has lived on the same block of Navajo Avenue in Balboa Park. Recently, she noticed a black gooey substance coming up all over her garage floor.

"I noticed more and more of this stuff coming up; like a greasy substance when you rubbed it," explains Paras. "Since then, we've gotten more and more."

She says most of her neighbors on this stretch of Navajo Avenue with eighteen homes have the same problem and worse, including strange and growing numbers of deep pits in the concrete slabs.

"I'm quite concerned because I don't want to live with contamination under my house," says Paras.

Paras says the city of San Francisco has been no help.

"They took samples; twice they came out. I called them and they said they'd get back to me. I never heard from them," says Paras. "Three months has gone by since I haven't heard."

The neighbors hired consumer attorney David Birka-White, who says he's already had surface samples analyzed and is now taking earth core samples.

"We've found there's a series of chemicals that come from bus maintenance and automobile maintenance," says Birka-White. "So we're looking in the immediate area to find where those sources could be."

So the neighbors here wonder, is the city blameless or deliberately ignoring a costly problem?

Because not two hundred feet uphill from this neighborhood are SF Muni's huge rail maintenance yards including a former bus maintenance facility.

"I think years ago they must have dumped oil or whatever and it's gradually been seeping down," Paras says.

This substance also seems be affecting the foundations of the homes in the area.

"I'm worried about the foundation of my home," says Paras. "If there's an earthquake, I don't want it falling down on me."

Wednesday Muni said it doesn't know what the substance is and referred KTVU to the City Sewer Department. The sewer department said it's a matter for the Health Department, while the Health Department theorized that the substance is antifreeze, but claimed it was up to the residents to figure out what it is.

The residents will know in about a week and they say they'll sue to fix their homes and protect their property values.

"People that pollute things have a responsibility to take care of it," says Birka-White

Whatever the source of this strange seepage, the neighborhood says it's long past time that the city take a more serious look at it and do something about it.