Authorities said Thursday that they had found the bodies of five musicians who were part of a Mexican regional music group and had been reported missing in the northern city of Reynosa, which is close to the Texas border.

The musicians had been missing since May 25 and were members of Grupo Fugitivo, a band that frequently performed at local dances and parties. The men were kidnapped at around 10 p.m. that night while driving in an SUV to a performance location, according to investigators from the Tamaulipas state prosecutor’s office who were investigating their disappearance. On the outskirts of Reynosa, their remains were discovered. Nine people suspected of belonging to a branch of the Gulf Cartel, which is heavily represented in the city, have been arrested, according to prosecutors.

The killings were not immediately explained by authorities, and they did not deny reports in the local media that the bodies had been burned. Their performance style, Mexican regional music, which includes a range of styles like cumbia and corridos, has recently become more well-known and is starting an international musical renaissance. Sometimes, young artists honor drug cartel leaders, who are frequently portrayed as characters similar to Robin Hood.

It’s still unknown if the group sang these kinds of songs or if the performers were just victims of the widespread cartel violence that has plagued the city. Some musicians, however, have had their visas revoked by the United States after the Trump administration accused them of glorifying criminal acts, and other musicians have received death threats from cartels.

On the evening of their kidnapping, the musicians’ final message to their relatives was that they were on their way to the performance. There was no more communication after that.

Tamaulipas, a state plagued by violence linked to cartels for a long time, was deeply outraged by their disappearance. People protested in the streets, families reported the missing people, and the public was asked for help.