The arena entrances reopened but the floor of Time Warner Cable Arena is closed to all but delegates.
Marc Friedland, convention volunteer, said over-capacity issues often happen at conventions.
"There is always more people in the building than can fit on the floor, but that's OK as long as they don't get on the floor," he said.
Asked why more credentials were printed than there is room in the arena, he said, "It takes a lot of people to run a convention."
Don Baer, who said he had a ticket to sit in Clinton's suite but couldn't get into the arena, said he was disappointed.
"I'm very disgruntled. You can quote me," he said. "I can't get in because I waited too long I guess. What are they going to do? Apparently the [fire marshal] shut it down," he said.
The 5th Street and light rail entrances to the arena had been shut down and no one was getting in for at least about an hour. Big crowds of people were waiting to enter.
Amy Harder contributed to this post.
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