CHESAPEAKE, Va. (WVEC) -- A fire that happened on Saturday at Hickory Middle School was ruled accidental by fire officials later that morning.

Lieutenant Anthony Barakat with the Chesapeake Fire Department said firefighters were called to the school just before 4 a.m.

Upon arrival, they found a portable classroom on fire. The flames were contained to the classroom and no other buildings were damaged, he said.

Barakat said the fire started at a heating unit on the exterior of the portable classroom.

The Virginian-Pilot reported Deborah Hutchens, the school's principal, wrote in an email to school staff "if you have a classroom in a portable area, you are not allowed on site until further notice."

The portable classrooms serve "hundreds of students daily." One of them is used as an additional lunchroom space for students at the school, according to the paper.

The Virginian-Pilot also stated Christie New Craig, a Chesapeake school board member posted on Facebook Saturday morning that "There will be no issues opening on Tuesday."

In reply to a request for more information, a spokesperson for Chesapeake Public Schools said: "We always monitor for safety. When we have the results of the fire dept. investigation, we will take any action necessary. The school administration will make appropriate adjustments to ensure that the instructional day will move smoothly.

"Our portables have the alarms that are required. We are not responding to any questions regarding the other details until we see the fire departments report."

No injuries were reported from the fire.