BURGOS, Spain – An investigation into a massive fire at a Campofrio plant is underway one month after the incident, The Associated Press reported.

Dogs trained to detect accelerants were brought onto the site. The dogs were not deployed earlier because of dangerous conditions at the plant which was gutted by the fire, according to AP. Reconstruction of the plant is expected to take two years.

The fire broke out Nov. 16, forcing the evacuation of the building and residents living near the plant. Public safety officials also closed a highway after thick black smoke seemed to cause a traffic accident.

Madrid, Spain-based Campofrio is Europe’s largest processed meats company. The company has 25 plants in eight countries throughout Europe and in the United States.