Arsonists set a series of fires early yesterday at an elementary school under construction in Anne Arundel County, causing an estimated $1.5 million in damage just three months before the school was scheduled to open, authorities said. They said three suspects were arrested.

A passing motorist reported the blaze at the future Marley Elementary School in Glen Burnie shortly before 3 a.m., said John Scholz, division chief with the county fire department.

Scholz said firefighters arriving at the school found flames coming from the roof. Nine smaller fires were located inside the building, he said.

Nearly 60 firefighters battled the blaze for about an hour. Scholz said two suffered from heat exhaustion; neither was seriously injured.

Fire officials estimated the damage to the $15.8 million school at $1.5 million, Scholz said. A schools spokesman, Jonathan Brice, declined to offer an estimate until the damage has been more thoroughly assessed.

At the time the fire was called in, Scholz said, county police were investigating a report of "juveniles throwing flammable liquid on passing motorists." Three Glen Burnie residents matching the description were taken into custody, then brought to the scene of the fires for questioning by investigators.

Authorities said three -- Charles Sawyer, 20, and two 17-year-old suspects whose identities have not been released -- were charged with second-degree arson, destruction of property, breaking and entering, and making false statements. Sawyer was being held last night at the Anne Arundel County Detention Center in lieu of $45,000 bond. The 17-year-old suspects, who were charged as juveniles, were released to their parents.

Brice said schools officials would evaluate the damage before determining whether the building could open as planned in December.

He said construction on the school, adjacent to another school, began last year. Brice said last night that the school system had not determined whether the juveniles are students in Anne Arundel County.