A local news source, Portal de Angola, reported on Saturday that three young men were detained after the attack.
According to the report, some 7,000 worshippers were at a venue on the outskirts of Luanda for the weekend-long convention.
Forty-three victims were rushed to the hospital, but no deaths have been reported.
A witness, Abraham Kituxi, told Portal de Angola that his sister-in-law was one of the first to collapse. She told him that she had smelled something foul before passing out.
Shortly thereafter, more people began collapsing, creating panic throughout the venue. Some witnesses called the police and firefighters, who assisted with evacuating the victims to Cazenga Municipal Hospital and Cajueiros Hospital.
Police arrested three suspects, and four are believed to be on the run. They could not identify the toxic substance, but noted that it was in containers of 750 thousand liters spread throughout the venue.