Takata Corp. has modified the composition of an air bag propellant that contains a volatile chemical at the center of a recall of millions of cars worldwide, the company told Reuters.

A Takata official, who did not want to be named but spoke on behalf of the company, did not specify how the recipe has changed, but said ammonium nitrate remained a part of the mix. He told Reuters the shift was part of its process of "kaizen," or continual improvement, and the company believed the new composition was safer than the one used before.

In response to a question, the official said: "There is no admission of a defect with the original version. There has not been any finding that ammonium nitrate or the earlier composition was somehow flawed. We changed the composition in an effort to improve quality."