A Plainville woman has been charged after authorities say she intentionally set fire to her apartment building Monday morning, displacing more than 20 residents.

The fire occurred at 71 Messenger St. around 5:15 a.m., according to the Fire Department.

The suspect, Heather A. MacKinnon, 61, was found in North Attleborough, the department said. She was charged with arson of a dwelling, malicious destruction of property and disorderly conduct.

She will be arraigned Tuesday in Wrentham District Court, NBC-10 in Boston reported.

While battling the flames, fire crews extinguished the blaze in an apartment. But large amounts of smoke and heat spread throughout the building, damaging it, the department said.

Residents were tested for smoke inhalation, the department said. No one was seriously injured. One pet was rescued and treated by EMS.

Plainville Fire Chief Robert R. Skinner said a secondary exit was added to the building’s second and third floors in recent years, a change that made a “positive difference” in the fire’s outcome.

Police and firefighters are still investigating the incident, the department said.