A ruptured gas line caused an explosion at the Southern Container factory Wednesday morning on South Rutherford Boulevard. TMP/P. Estes-Simpson

An explosion reported shortly before 9 a.m. this morning near the Southern Container factory on South Rutherford Boulevard was caused by a boiler, authorties said.

First responders headed to the RockTenn Company at 8:45 after a steam recycling tank exploded inside the Southern Container building, Murfreesboro Fire Department Assistant Chief Allen Swader said.

"Luckily there were no injuries and no one was hurt," Swader said.

Initially officials thought a ruptured gas line caused the explosion, which led to the closure of South Rutherford Boulevard and the CSX tracks.

Swader said the explosion did compromise a six-inch gas line but Atmos Energy shut off the line quickly. A mysterious substance also was found near the explosion but a hazmat team neutralized it with soda ash.

The explosion was felt as far away as Warrior Drive and the Public Square.

Murfreesboro Building Codes is inspecting the damaged part of the building and Tennessee's Division of Boilers, Elevators and Amusement Devices is looking into the cause of the explosion.

More than 100 people are employed at the Southern Container facility. Most have been allowed to return to work, Swader said.