The Food and Drug Administration has asked the Drug Enforcement Administration to assist in its investigation of a vaping illness that's caused hundreds of people to fall ill in recent weeks, killing at least nine patients.

The health regulator also said it will pursue criminal charges against anyone who makes or sells e-cigarettes that have been tampered with and cause anyone to get sick.

"To be clear, if we determine that someone is manufacturing or distributing illicit, adulterated products that caused illness or death for personal profit, we would consider that a criminal act," acting FDA Commissioner Dr. Ned Sharpless testified before the House Energy and Commerce subcommittee on Wednesday. He said the FDA's probe is focused on vaping manufacturers, "following the supply chain to its source," not on individuals who've used the products.

Sharpless said the agency has called on the DEA for help because a number of the deaths have stemmed from people who've vaped THC, the ingredient in marijuana that produces a high.

The FDA recently issued a warning letter to Juul Labs for marketing unauthorized, modified tobacco products, including at a presentation to children given at a school.

The agency said last week it would be opening up a criminal probe into the cause of the mysterious vaping-related lung disease, which resembles a rare form of pneumonia. Hundreds of people have become sick from it so far, with nine people dying in recent weeks.

But many lawmakers have blamed the spike in teen e-cigarette use on the FDA's 2017 decision to delay the review of the products.

In retrospect, "the FDA should've acted sooner," Sharpless said. The accelerated investigation should help the agency "catch up," he added.

The Centers for Disease Control and Prevention told consumers to avoid all vaping products as health officials work to figure out what's making people sick.

— CNBC's Elijah Shama and Angelica LaVito contributed to this article.

Correction: This article was updated to reflect the correct name of the Drug Enforcement Administration.