SAN JOSE -- As students in an Evergreen Elementary classroom prepared for a field trip Wednesday, a squirrel with a different set of plans entered the classroom and attacked a first-grader and two adults.

A call came in to 911 at around 8:43 a.m. reporting a squirrel attack on an seven-year-old girl and two field trip chaperones. The attack was severe enough to draw blood from the arm of at least one of the adults, according to San Jose police Sgt. Nick Muyo.

All three were treated at the school and paramedics arrived later. The victims suffered scratches and possibly bites but are OK and did not require hospitalization, said Will Ector, spokesman for the Evergreen Elementary School District.

The classroom door was open when the squirrel entered the classroom.

"We took immediate precautions to ensure the security of our students," Ector said.

All classrooms were ordered to close their doors and staff and students were alerted to the situation. Children are also being kept away from areas frequented by squirrels.

Ector said the attack seemed unprovoked.

The school does not have a high squirrel population nor a history of squirrel attacks, he said.

Humane traps have been set by the school's animal control partner to catch the brazen critter, which remains on the run, he said.

Squirrels do not often attack people and when they do it usually has to do with food. At certain times of the year and under certain conditions squirrels can get aggressive, said Russ Parman, a Santa Clara County Vector Control District assistant manager.

As far as rabies goes, Parman said squirrels are not often associated with the disease and are a low-risk animal when it comes to transmission of the viral illness, which is usually transmitted to humans through the bite of an infected animal.

"Generally speaking, squirrels are not the type of animal that can survive an attack by a rabid animal," Parman said. "They are prey animals."

Testing "never hurts," Parman said, with regard to the status of the squirrel and its victims in today's attack.

Recent squirrel attacks in Mountain View were likely the result of overzealous and hungry squirrels and their conditioned response to those who feed the animals.

Explaining how an adult might be injured, Parman said that when squirrels are scared they will try to climb -- and that sometimes they'll climb people to escape.

Evergreen Elementary School is located at 3010 Fowler Road.