While no cause had been determined for the recent fire at the Douglas Macarthur Elementary School, the fire alarms are working, according to the Waltham Fire Department.

“The system is operational and is functional,” said Waltham Fire Lt. Michael Murphy, during an interview with Waltham Patch yesterday.

In response to previous reports that the alarms did not sound, Murphy said that happened because the fire never actually entered the building to cause enough heat and smoke for them to trigger.

“The reason the fire alarm did not activate … is because the fire was on the roof and there are no fire detectors on the roof,” Murphy said.

The building alarm system, he said, meets standards set by the National Fire Protection Agency. The alarms, he noted, are regularly tested and are working.

As for the cause of the blaze, Murphy said the Waltham Fire Department is working with the state Fire Marshal’s office to figure out the cause.

The department routinely collaborate with the fire marshal’s office because it has additional resources that help investigate causes, Murphy said.

The Waltham Public Schools have already announced they are taking several steps to addresses issue raised by the fire, including the solar panel system in which the fire started.