People driving along Colo. 128 south of Boulder are confused by what some are calling a combination of a bullet and a missile.

Several passersby said the huge, silver projectile has been set up on a long arm extending from the back of a Ball Aerospace pickup truck on the north side of the highway since Monday, according to Boulder County News.

Mark McDade, who works at the National Wind Technology Center close by, pulled over on Wednesday to see what was going on, and the people at the site told him that they worked for aerospace companies Ball and Lockheed Martin.

"I asked (one person) if it was military technology, and he said 'No.' Then I asked him if it was commercial proprietary, and he literally kept his mouth shut," McDade said. "The hush-hush nature of the whole thing is what really got me curious."

The object also caught the attention of Lakewood resident John Henry, who was driving from Broomfield, Colorado when he saw it and described it as a "bullet-looking missile thing," The Blaze reported.

Henry said he saw another one eight miles down south, saying that while he didn't know what it was, he wasn't "too worried about it."

The workers didn't reveal much information to motorists and cyclists that pulled over to ask about the object, as one man only said they were doing "engineering testing" without giving his name or saying who he or anyone else at the site was working for, Boulder County News reported.

However, Ball officials provided a taste on Thursday of what was going on, saying they are a subcontractor on the project while avoiding specific questions.

Suzanne Smith, spokeswoman for Lockheed, said the company got permission from the Colorado Department of Transportation to test the sensor technology, and that funding is coming from the company.

Testing was completed on Thursday, and information about the nature of the tests was "competition-sensitive."