Health and Human Services Secretary Robert F. Kennedy Jr. said Thursday that the cause of the autism epidemic in the U.S. will be uncovered in a few months, despite years of research being unable to find one.

Mr. Kennedy made the bold proclamation during a cabinet meeting with President Trump on Thursday. “By September we will know what has caused the autism epidemic and we will be able to eliminate those exposures,” Mr. Kennedy said.

Mr. Kennedy said hundreds of scientists around the world are working together to find the cause. “We’ve launched a massive testing and research effort,” Mr. Kennedy said. “There’s got to be something artificial out there that’s doing this,” President Trump responded. “Something’s causing it.”

Scientists have been working for decades to try to find what factors might contribute to autism but the cause or causes remain unclear. Mr. Kennedy has long blamed vaccines for autism. He once claimed there was a link between the condition and a preservative that is used in vaccines. He later claimed MMR shots caused a spike in autism cases.

Dozens of major studies have found no connection between MMR vaccines and autism. During his confirmation hearing, Mr. Kennedy would not say that vaccines do not cause autism.

Studies have shown autism likely begins in the womb, before any vaccines are given to children. Mr. Kennedy said Thursday that the number of autism cases continues to rise and 1 in 31 children are now  diagnosed. He claims that it was 1 in 10,000 when he was a child although it is unclear where that number came from.

Autism wasn’t listed as a separate diagnosis until 1980,  the year Mr. Kennedy said the cases of the affliction began rising. The American Academy of Pediatrics only started recommending screening all children for autism during routine pediatrician visits in 2006.

There is speculation that autism rates have simply grown as doctors spend more time looking for it and diagnosing the condition.