Fire Investigator Lennis Harris couldn't say the houses at 1103 and 1105 Simmons St. were total losses. That determination is left up to housing inspectors, he said.

But the veteran fire investigator did say he was shocked to see the size of the flames roaring simultaneously from two homes when he arrived at the scene around 10 a.m. Tuesday.

"When I pulled up and saw the amount of fire in both houses, I could not believe both houses were still standing," he said.

Harris said the fire, which he termed "suspicious," began at 1105 Simmons St. and quickly spread to the structure next door.

Both houses, valued around $40,000 on city property records, were vacant, Harris said, and neither had electricity when the fire broke out.

The homes are the fourth and fifth abandoned houses in this block to succumb to large blazes this year. Firefighters fought a similarly large blaze on Colfax Street in March, where a fire at one vacant home quickly spread to the vacant house next door.

Neighbors told firefighters at Tuesday's fire that the homes were the stomping grounds for vagrants and drug users. The owners of both structures, according to property records, are absentee landlords.

Benjamin Young of Washington, D.C., owns 1103 Simmons St. Sharon Denise Lockett of Bayonne, N.J., is listed as the owner of 1103 Simmons St. Attempts to contact both owners were unsuccessful Tuesday.

Some fires in vacant homes occur when vagrants try to keep warm, but Tuesday's fire appeared to be "no accident," Harris said. The exact cause of the fire is still under investigation, he said.

Asked about the number of vacant house fires in Durham this year, Harris said he could only advise owners of vacant homes to do their best to secure their properties and to attempt to make the houses look "lived in." Abandoned homes have long been a problem in Durham, he said.

Gary Kueber, historic home preservationist and the author of the blog "Endangered Durham," said the recent rash of vacant home fires indicated the city needs to find a better way to deal with long abandoned homes.

The current means of dealing with vacant homes is simply to destroy them, he said.

"We need a third way" between bulldozing homes with historic value and letting abandoned, degenerating properties fester, Kueber said. "Other cities have better tools to deal with this," he said.

Attempts to reach City Manager Patrick Baker for comment were unsuccessful Tuesday.