GENEVA — A $2 billion experiment on the International Space Station is on the verge of explaining one of the more mysterious building blocks of the universe: The dark matter that helps hold the cosmos together.

An international team of scientists says the cosmic ray detector has found the first hint of dark matter, which has never yet been directly observed.

The team said Wednesday its first results from the Alpha Magnetic Spectrometer, flown into space two years ago, show evidence of a new physics phenomena that could be the strange and unknown matter.

Nobel-winning physicist Samuel Ting, who leads the team at the European particle physics laboratory near Geneva, says he expects a more conclusive answer within months. The findings are based on an excess of positrons— positively charged subatomic particles.

“This is an 80-year-old detective story and we are getting close to the end,” said University of Chicago physicist Michael Turner, one of the giants in the field of dark matter. “This is a tantalizing clue and further results from AMS could finish the story.”