Hazmat crews responded to the Metro Central transfer station in northwest Portland on Wednesday.
Portland Fire & Rescue reported a 55-gallon drum was leaking an unknown material and small explosions were heard inside the building.
Crews arrived at the scene around 11:30 a.m.
The garbage, recycling and hazardous material waste disposal site is on the 6100 block of Northwest 61st Street. Firefighters said the building was evacuated due to the leak.
No other evacuations were deemed necessary, according to firefighters. The Portland Bureau of Transportation advised drivers that traffic would be affected between Northwest Front Avenue and St. Helens Road.
By 1 p.m., hazmat technicians determined the product that leaked was likely benign and "initial concerns are calmed."