Ever since a huge crater was discovered off Mexico's Yucatan Peninsula in the early 1990s, scientists have been confident that an asteroid slammed into Earth 66 million years ago and killed off the dinosaurs and most life on the planet.

The cause has never been definitively settled, and some scientists have questioned the widely held "sudden-death by asteroid" theory. That camp believes that massive volcanic eruptions, which may have released climate-changing gases in the Spain-sized region known as the Deccan Traps, played a significant role.

Now, a group of researchers at Yale University are putting the blame back solely on the asteroid, CNN reports.

They say that any environmental impact from the eruptions and lava flows that occurred in the Deccan Traps (located in what is now India) happened well before the extinction event that wiped out the dinosaurs, which scientists call K-Pg.

"A lot of people have speculated that volcanoes mattered to K-Pg, and we're saying, 'no, they didn't," said Pincelli Hull, an assistant professor of geology and geophysics at Yale and lead author of the study, which published Thursday in Science.

"What our study does is take 40 years of research and adds a bunch of new research. It combines this in the most quantitative tests you can do and it really doesn't look like it (was the volcanoes)."

Some researchers believe that emissions from the volcanoes, which released gases like sulfur dioxide and carbon dioxide, weakened the ecosystem so that dinosaurs went extinct more easily when the asteroid hit.