Since 2007, scientists have detected 22 fast radio bursts (FRBs), a type of super-high-energy signal from space. The problem is, they have no idea what the signals are or where they come from. Now they've detected another—and it's only further deepened the mystery, reports Ryan F. Mandelbaum for Gizmodo.

Dubbed FRB 150215, this latest burst came in February 2015. The research community scrambled to coordinate 11 different telescopes and instruments across the globe immediately after its detection to search for anything associated with the burst. But they came up empty handed.

“We spent a lot of time with a lot of telescopes to find anything associated with it,” Emily Petroff, astrophysicist at the Netherlands Institute for Radio Astronomy and first author of a study on the FRB that appears on the preprint server arXiv.org, tells Mandelbaum. “We got new wavelength windows we’ve never gotten before. We looked for high-energy gamma rays and neutrinos...we ruled out some source classes but no detection is a little unhelpful. We’re still trying to figure out where this one came from.”

In fact, Mandelbaum reports, it was unlikely researchers would've spotted FRB 150215 in the first place—the signal should have been blocked or altered by our galaxy's magnetic field. To get to Earth, the FRB may have traveled through some previously unknown hole, Petroff tells him.

So what do researchers think the bursts are? Scientists joke that there are more theories than there are recorded FRBs, and they are only half-kidding. Hannah Osborne at Newsweek reports that the bursts could be caused by neutron stars collapsing into a black hole or that they are caused by a highly magnetized neutron star. One recent, and controversial study, raised the possibility that the bursts could be coming from advanced propulsion systems used by an alien civilization to power interstellar travel, though Petroff strongly doubts the idea.

And though the cause is still unknown, researchers have made some headway in investigating FRBs. In January a paper was released tracing FRB 121102, the only FRB that has repeated, to a dwarf galaxy in the Auriga nebula.

But this latest paper, though important, doesn't yet help sort out the mystery. “I have to say this is a fantastic paper but it is a bummer of a paper,” Shami Chatterjee, senior research associate at the Cornell Center for Astrophysics and Planetary Science tells Mandelbaum.“They threw every resource that we have at this FRB...and they see nothing." Chatterjee adds, however, that the study is important in showing that there isn't obvious afterglow or effects immediately after the burst.