Sep 26, 6:04 PM EDT

Mexico arrests 3 who carried out grenade attack

MEXICO CITY (AP) -- Mexican federal prosecutors say they have arrested three men who they believe carried out a grenade attack on an Independence Day crowd that killed eight people.

Officials say the men confessed to throwing the grenades and being part of the infamous Gulf Cartel hit-men group known as the Zetas.

The explosions on the night of Sept. 15 ripped through crowds of holiday revelers in the western city of Morelia. Drug gangs were immediately suspected. But it remains unclear why they would target seemingly innocent civilians for the first time.

Prosecutors announced the arrests Friday at a news conference in Mexico City. They say the men were detained Thursday ... TE=DEFAULT