Rogue emissions of a gas that harms the ozone layer are coming from eastern China, primarily from two heavily industrialized provinces, an international team of researchers said Wednesday.

The findings confirm what many scientists, environmental groups and policymakers had suspected after an initial study a year ago reported new global emissions of the gas, CFC-11, but could only locate the source generally as East Asia.

The new research will add to international pressure on the Chinese government to curtail the illegal use of CFC-11. It also confirms the results of several investigations, including one by the New York Times, which found evidence that factories in Shandong, one of the provinces specified in the study, were still making or using the gas to manufacture foam insulation.

CFC-11 is one of a class of compounds called chlorofluorocarbons that destroy atmospheric ozone. They are also potent greenhouse gases that contribute to atmospheric warming.

Chlorofluorocarbons were outlawed for almost all uses by the Montreal Protocol, an international pact negotiated decades ago to preserve the layer of ozone that blocks ultraviolet radiation from the sun. Excessive amounts of some types of UV radiation can cause skin cancer and eye damage in people and are harmful to crops and other vegetation.

After the initial study last year, China denied that there were serious violations of the ban on the chemical but also promised to eradicate any illegal production and use.

The Chinese Ministry of Ecology and Environment said Wednesday that it was preparing answers to questions about the new findings that the Times sent last week.

In a statement, Joyce Msuya, acting executive director of the U.N. Environment Program, which administers the Montreal Protocol, said that action on CFC-11 “is being taken by all parties at the international level and by China domestically.”

“All parties appreciate the urgency to ensure the ongoing protection of the ozone layer,” she added.

The declines in chlorofluorocarbon emissions under the Montreal Protocol were expected to lead to a full recovery of the ozone layer by the middle of the century. The new emissions could delay that recovery by a decade or more, scientists say.

The study, which was published in the journal Nature, used data from monitoring sites in South Korea and Japan that analyze air samples taken every few hours. The data was fed into computer simulations that model how the atmosphere disperses pollutants.