(CNN) Vitamin E acetate, an additive sometimes used in THC and other vaping products, may be to blame for a national outbreak of e-cigarette-related lung injuries that's linked to dozens of deaths, according to US Centers for Disease Control and Prevention officials.

Dr. Anne Schuchat, the principal deputy director of the CDC, said she would characterize it as a breakthrough in the agency's investigation, although more tests are necessary.

"These new findings are significant," Schuchat said during a press briefing on Friday. "We have a strong culprit."

There is still more work to do and the CDC said it is continuing to test for a wide range of chemicals.

"This does not rule out other possible ingredients," Schuchat said. "There may be more than one cause."

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