A cigarette discarded by a teenager ignited last week's six-alarm blaze in downtown Ellicott City that caused more than $2 million in damage, investigators concluded yesterday.

The fire was ruled an accident by the state fire marshal and the Bureau of Alcohol, Tobacco and Firearms, which routinely aids the state in investigations. No charges will be filed against the 17-year-old cook at the Main Street Blues Cafe, who investigators said threw an unextinguished cigarette on or near a pile of trash and cardboard boxes just outside the rear of the cafe.

The teenager soon smelled smoke and helped evacuate two people from the building before the fire spread.

"As far as we're concerned, the case is closed. It was a tragic accident," said state fire marshal spokesman Allen Gosnell, adding that the teenager was cooperative with investigators.

The fire, which took more than 12 hours to bring under control, destroyed several apartments, gutted four buildings and damaged two others. No one was injured. The historic Main Street district of Ellicott City, with its quaint coffee shops and antiques dealers, was open for business yesterday, save for the six damaged businesses.

Demolition of the upper levels of the damaged buildings continued yesterday.

Though criminal charges will not be filed, civil lawsuits by affected business and building owners are likely. Lawyers for several said their insurance companies will decide whether to file suit--and whom to sue. They said the teenager at fault was not a probable target.

"Suing the teenage cook is like spitting in the wind to put out the fire," said Ronald Spahn, an attorney for the family of Ellicott City physician Bruce Taylor, owner of one of the most severely damaged buildings, which housed three businesses. " . . . You might look at whoever insures [Main Street Blues] to collect from."

William Sachs, an Ellicott City artist and co-owner of the Spring House Design art store, which was moderately damaged in the fire, said he will not consider suing anyone. This despite discovering over the weekend that he has a limited insurance policy that will not begin to cover the total repair costs.

"What gain would there be from suing? These are members of the community," he said.