"The beat was about to drop, and literally the whole floor collapsed," one witness said.
Three rafts flipped on the Naranjo River on Saturday afternoon, and the five victims were carried away downstream, according to authorities.
The incident, in which no one was injured, "revealed a potential for the battery inside the camera to ignite," police said.
"I know folks are scared and hurt. So am I. We are working to stop this and we will never give up," Chase Strangio, an attorney with the ACLU, tweeted.
The five helicopter passengers drowned when they were unable to free themselves from their harnesses.