Demolition of the historic Sigma Phi Epsilon fraternity house at 237 Langdon St., destroyed by fire in the early morning hours of May 13, is scheduled to start in mid-October, contractors say.

The police tape is gone, the residents have been relocated in a fraternity house across the street, and the now uninhabitable 8,000-square-foot house has been released to its owners, the Wisconsin Beta Chapter of Sigma Phi Epsilon, but Madison fire investigators have yet to nail down the cause of the fire.

Last week, the City Plan Commission approved the fraternity's request through its contractor, Executive Outcomes of Fortville, Ind., to demolish what's left of the building. Contractor Thomas Hurlbut on Friday said a settlement with the fraternity's insurance company is expected at the end of this month, after which site work can start.

But there's still no word on what caused the dangerous blaze. Though the scientific evidence is all in, Madison fire investigators say they are stalled by the difficulty in finding people to interview. "Once people start to disperse, communication really kind of slows down," said Madison Fire Department Captain Bradley Olson. "There's no blame as far as why we are not getting information."

The fire occurred during finals week at the UW-Madison, Olson said, and possible witnesses left town soon after the fire.

Shortly after the fire, UW-Madison Dean of Students Lori Berquam said students who fled the house told her the fire began outside at the back of the building. Olson refused to confirm that this week -- or release any other facts about the fire. It might jeopardize future interviews, Olson said.

So, for now, the Sig Ep blaze is one of 28 cases still active from 2007, out of 139 investigations done that year by Madison Fire department investigators. Another 24 cases from that year are inactive. Olson said they've hit a dead end, with new leads unlikely.

And 42 were identified as arson, he said. The Sig Ep house could be one of those. "It might be a set fire," Olson said. "It might be accidental. Too many pieces are unknown."

Fire officials estimated the damage to the three-story building and its contents to be at least $750,000. According to the 2008 tax assessment, the property is valued at $742,000.

Madison City Zoning Administrator Matt Tucker said the approval included several conditions: regrading the site and seeding it, removing the driveway, properly capping the sanitary sewer and removing the water meter and having a reuse/recycling plan reviewed and approved by the city.

"All conditions must be satisfied before an actual permit to remove the building will be issued," Tucker said. "It may take a couple of weeks."

The fraternity said it plans to rebuild on the same site though the permit application specifies "no proposed reuse at this time."

The house had been occupied by Sigma Phi Epsilon since 1995. Built in the early 1890s with two stories, the top levels were added in 1910 by a university professor.

Ryan Sugden, vice-president of operations for the Sigma Phi Epsilon Alumni Board, said about 20 fraternity members are now sharing space in the Tau Kappa Epsilon fraternity house.