Dozens have been reported injured after the floor of a second-story garage apartment collapsed during a Jainist celebration in a Houston suburb. According to reports, at least 100 people had gathered for the party with a religious leader visiting from India and that people on the first floor were trapped after the ceiling above them caved in.
KHOU reports that one person is being treated for a serious head injury and that at least 30 people were being seen at area hospitals for varying injuries. Among the injured was an eight-year-old boy.
According to USA Today, the floor collapsed for exactly the reason you thought: there were too many people.
The second floor was designed to hold six people and there were as many as 40 people upstairs when the floor collapsed onto the lower section. The collapse trapped people underneath and injured those who were above.
Additionally, in aerial views of the garage you can see "signs of rippling or buckling."