ELLICOTT CITY, MD., NOV. 23 -- Just about everybody -- residents, property owners, state fire investigators -- has a theory about the mysterious rash of arsons on Main Street.

But so far, authorities have been unable to apprehend anyone responsible for six of the nine fires in the 8400 block of Main Street since July 26. One vacant house has been torched seven times in the past five months, fire officials said.

Luckily, no one has been injured in the fires, but residents are fearful of the worst.

"I look out my window every night before I go to bed," said Mary Miller, who lives in a 10-room house at 8483 Main St. with her daughter and two grandchildren.

Neighbors said they fear the fires in the old row houses could be deadly because they spread so fast.

"It worries me," Miller said. "If they don't catch the person, something bad is going to happen."

The buildings are a short distance from the Ellicott City fire station, and firefighters have been able to quickly extinguish the blazes, said Howard County Fire Cmdr. Donald Howell.

But Deputy State Fire Marshal John Earp said the fires are "getting progressively worse."

On Sunday, a Main Street fire caused serious damage to the inside of the nearly 100-year-old vacant house that has been set on fire seven times since July, and an adjacent structure had minor smoke damage from the blaze, Howell said. Fire officials estimated damage to the house to be $3,000.

The building at 8740 Main St., owned by Historic Ellicott City Properties, seems to be the main target of the arsons, fire officials said.

Authorities arrested a neighborhood man late this summer in connection with three of the fires, Howell said.

The first fire, on July 26, occurred three days before a tenant was scheduled to move into the recently renovated building, said Steve Maben of First American Management, a local realty company that manages the building.

Two more fires were set the next day at the wood frame house, fire officials said. An arsonist struck again on July 31, authorities said.

The next fire occurred Sept. 20, followed by another Oct. 2 and the most recent on Sunday.

Maben said the old house probably will have to be razed because of extensive fire damage, which he estimates at $70,000 from all of the blazes.

The fires have gutted the roof, kitchen, living room and back porch of the hillside house, he said.

Like other residents in the area, Maben has his own theories about who may be responsible for the arsons.

"It may be something personal," Maben said. "Or, who knows, there are a lot of crazy people in the world."

Deputy Chief State Fire Marshal Bob Thomas said fire investigators believe the last six fires are the work of one person, probably "someone very familiar with the area and who lives nearby."

All of the fires have occurred between 3 and 6 a.m., Thomas said.

Authorities believe the fires are being set by a "vanity fire setter," a person trying to attract attention for selfish or monetary reasons, Thomas said.

Yesterday, frustrated residents said they just want the arsonist caught -- soon.

"I'm angry that they {police} have been unable to catch a suspect," said Barbara Shulte, whose house at 8472 Main St. was damaged in Sunday's fire.

But Shulte, who along with her husband James recently moved out of the 60-year-old house, said she was most angry "that someone would be stupid enough to do this. If the fire had happened Friday night with those high winds, it would have been even worse."