CHICAGO – A woman was charged Monday with arson and murder for allegedly setting a series of house fires near Wrigley Field, including one that killed four people.

Witnesses had reported seeing an unkempt woman wearing clear plastic bags as shoes near three small fires that broke out in the area late Friday and early Saturday, according to Edward O’Donnell, commander of the police department’s bomb and arson unit.

The fourth blaze, reported Saturday morning within walking distance of the others, killed four people in a three-story apartment house. It was started with paper debris on a stairwell landing between the second and third floors, fire officials said.

Mary Smith, 43, was questioned after the fires and charged Monday with two counts of aggravated arson and four counts of first-degree murder, the Cook County state’s attorneys office said.

Police had brought the woman in for questioning late Saturday after finding her with “an odor of smoke,” police spokeswoman Monique Bond said.

Police Cmdr. Thomas Byrne said Smith, arrested in a coffee shop, made self-incriminating statements, and witnesses identified her from “numerous” lineups. She appeared coherent and calm, he said.

He said police did not know a motive for the alleged arsons.

Three of the victims were men in their 20s, police said. The fourth victim was Jennifer Carlson, 24, said her aunt, Cheryl Greenlee.

Witness statements and other evidence linked Smith to the smaller fires, police said. One of the arson counts is connected to one of the smaller fires.

O’Donnell said one small fire was started with papers in a building stairwell, a sweater was set on fire on a sidewalk and the third was set with papers on a front porch. A homeowner extinguished one of the fires, and the other two were extinguished by the time firefighters arrived, he said.