The sale price represents an enterprise value of $62 million.
Enaex is a subsidiary of Chilean company Sigdo Koppers Group, which has operations in five continents, and is the largest producer of explosive-grade ammonium nitrate in Latin America.
Downer CEO Grant Fenn said the sale of the blasting services business was an important step in the company's strategy to focus on urban services.
"The sale of Downer Blasting Services follows the sale of the Snowden consulting business and also our share in the RTL Mining and Earthworks joint venture," he said.
"We are in active discussions with a number of interested parties in relation to the rest of the mining portfolio."
The transaction is expected to close by March 2021.
Downer shares last traded at $5.20, valuing the company at $3.6 billion.
