ALAMEDA -- An arsonist ignited a stack of books at Alameda High School early Wednesday morning, causing minimal damage inside a classroom before firefighters extinguished the blaze, police said.

No one was hurt and classes continued as scheduled on Wednesday.

Investigators suspect the arsonist may have entered the ground-floor classroom, which is used by an English teacher, through an unlocked window because they found no sign of forced entry, Alameda police Lt. Ted Horlbeck said.

Firefighters were dispatched after a smoke alarm was tripped about 3:26 a.m., and crews quickly located the classroom because the alarm system also shows where on the campus smoke has been detected, Horlbeck said. The books that were set alight were stacked on a table.

The damage was minor and contained to just the small area of the classroom, Alameda fire Capt. Jim Colburn said.

Firefighters put out the fire with extinguishers, Horlbeck said.

Colburn said he was not aware of any recent arson fires that could be connected to Wednesday's blaze.

Teachers and administrators at the school at 2201 Encinal Ave. also said they have not had any issue with a student that would indicate someone was possibly planning to set a fire, Horlbeck said.

It was not immediately clear whether the arsonist used an accelerant.