Italian Filippo Di Pierro was "arrested and questioned" a police source told AFP on Tuesday, adding that the investigation is ongoing.
Eldense player Cheikh Saad was the first to point the finger at a number of his teammates and coach.
Saad told radio station Cadena Copa that certain players stood to make "huge sums" of money from bets placed on the match.
The club's president David Aguilar then reported his suspicions to the police and the Spanish football authorities.
Di Pierro was appointed as coach after an Italian investor took control of the club earlier this season with suspicions now raised over whether that investment was linked to illegal betting patterns.
"At the very least, we must investigate it because there are certain links to an Italian group that has the look of what may be indications of a international betting ring when it comes to fixing matches," said president of the Spanish league Javier Tebas.
There is no suspicion of wrongdoing on the part of Barca B and Barcelona boss Luis Enrique believes they have been "victims" in the case.
"It is a delicate subject that has to be handled seriously," said Enrique.
"Barca B are not implicated, they are simply victims of this type of blackmail. It is good they are being pursued and we can get this out of football as soon as possible."