A pressurized tank exploded Monday in a Virginia building inhabited by a defense contractor that makes rocket launchers for the military.

The blast lead to evacuations and a robust response by local emergency crews to 9441 Innovation Drive in Manassas, a worksite used by defense contractor Utron.

One male employee suffered a minor injury after a large pressurized cylinder launched through the roof and crashed back into the building in another area, Fire Marshal Curtis Brodie told News4's Julie Carey, creating "substantial" damage inside.

The injured man was transported to a local hospital with minor injuries. He suffered abrasions and other injuries due to the release of the cylinder, Brodie said.

The vessel created a four-foot hole through the roof at its exit.

"I was just sitting in my cubicle, working on engineering stuff when all of a sudden, there was this loud boom," said Dylan Pizzitolo, an electrical engineer at the adjacent Nikon Metrology office space. "And I thought it might be have been thunder or it might have been an earthquake, or something like that, and then I heard another boom a few seconds later, and I got concerned and left the building."

The object left a large debris field, and parts of the roof littered the parking lot, breaking car windows and denting other vehicles.

Pizzitolo said someone at Nitron pulled a fire alarm, and a group of people left the building to see smoke coming out of the complex's garage.

"And there was pieces of rock all over the floor, the ground.... The glass got blown out, some people's cars," he said. "It was basically just glass damage, glass damage in front of the building. Some things got shattered, rocks, gravels, the roof material."

Employees at Nikon said even in their section of the complex, ceiling tiles were shifted and some light fixtures were dropping from the ceiling.

The Prince William County Fire Department and Manassas Volunteer Fire Department were called to the scene, as were a hazmat team and the Prince William building collapse rescue team.

Almost 40 units responded in all, said the Manassas Volunteer Fire Department.

Officials have determined there are no hazardous chemicals present. The building department is now inspecting the structure to determine whether it is safe to enter.

The building has been evacuated shortly after the blast. There is partial damage to the building and to the roof.

According to Utron's website, the company is a compacted-powder parts manufacturer that develops products for the defense and aerospace industry. Past and present clients include the U.S. Navy, the U.S. Army, NASA, the Ballistic Missile Defense Organization and others, according to Utron's website.

Stay with NBC4 and NBCWashington.com for more.