(York) -- Investigators say a fire in York County that badly damaged four row homes and displaced 12 people was intentionally set.

The fire broke out shortly before 11:00 a.m. Wednesday in York.

Fire Chief David Michaels says the blaze was started in a small breezeway between two of the homes.

Firefighters said a mattress and trash was found in the narrow space where the fire began.

Witnesses reported seeing two teenagers running from the breezeway and laughing shortly before the fire broke out.

The American Red Cross said it was assisting the four families who were displaced.