REVERE – Two firefighters were sent to the hospital and a hazmat scene has been declared after a fire at a candy factory in Revere caused a leak of a dangerous chemical on Friday.Revere District Fire Chief Glen Rich said a fire broke out around 11 p.m. in the mechanical room of the New England Confectionery Company, a candy company better known by its acronym NECCO, at 135 American Legion Highway.Rich said the fire started in the mechanical room of the building, which is always monitored by an employee because it contains tanks of a potent kind of ammonia commonly used for refrigeration and food preservation.”It’s pretty bad stuff,” Rich said.He said the employee called the fire department immediately, but as firefighters rushed into the building they were overcome by fumes from ammonia, which had begun to leak. Two firefighters passed out and were taken to Massachusetts General Hospital, where they were treated with oxygen.Rich said they were released later in the night are are doing fine.As other fire crews put out the fire, a state hazmat team responded and shut off valves controlling the ammonia. But they deemed the building contaminated and are letting it ventilate today, Rich said.He said fire investigators don’t know what caused the fire or the extent of the damage and won’t be able to investigate until hazmat teams give the OK to re-enter the building.He said that people near the building or driving by on American Legion Highway aren’t in any danger because the ammonia is relegated to inside the candy factory.”There is no risk to the public at all,” he said.A call to NECCO headquarters was not immediately returned.Nearby in Lynn, two people died in an early-morning house fire.