A large plume of black smoke lingered in the East Hampton Village sky on Tuesday morning, though the cause sent fire department personnel back to the firehouse quickly.
The "puff-back" from a furnace occurred at the on Newtown Lane at around 6:45 a.m.
Chief Ray Harden said he knew exactly what it was as he approached the building and saw the smoke. "It seems like it happens once a year there," he said.
There are two large boilers at the school, Harden said. A puff-back, which is a premature explosion inside an oil furnace, causes a large amount of smoke, and soot, to be released.
Harden sent fire engines and ambulance personnel back in service soon after the call.
Middle School Principal was not immediately available as students were given testing on Tuesday morning.