Scientists described the case as a "mystery" but remain skeptical that the signal could be caused by intelligent aliens.

"In case you are wondering, the recurrent aliens hypothesis is at the bottom of many other better explanations," Abel Mendez, director of the Planetary Habitability Laboratory at the University of Puerto Rico, said in a blog post.

Researchers at the Arecibo Observatory in Puerto Rico first recorded signals coming from a group of nearby red dwarfs in April and May. After analyzing them, they noticed "some very peculiar signals in the ten-minute dynamic spectrum that we obtained from Ross 128," Mendez said.

"We believe that the signals are not local radio frequency interferences since they are unique to Ross 128 and observations of other stars immediately before and after did not show anything similar," the scientist added.

The research team came up with several possible explanations for the signals from the celestial body, which is only 11 light-years away from Earth. The most likely options are that the signal originated due to emissions similar to a Type II solar flare, that it was sent from another object in the field of view of the star, or by a high-orbit satellite.

"Each of the possible explanations has their own problems," Mendez said in his blog post. "For example, Type II solar flares occur at much lower frequencies and the dispersion suggests a much farther source or a dense electron field (e.g. the stellar atmosphere?). Also, there are no many nearby objects in the field of view of Ross 128 and we have never seen satellites emit bursts like that," he added.

In a bid to clarify the issue, the team from the Arecibo Observatory enlisted the help of astronomers from SETI (Search for ExtraTerrestrial Life), who will use the Allen Telescope Array and the Green Bank Telescope to observe the star on Sunday, according to the US magazine Newsweek .

The results are to be published later this week.