All tickets to next month's opening weekend of the National Museum of African American History and Culture were snapped up within the hour they first became available Saturday morning, as were passes for the following two weekends.

Smithsonian officials said 28,500 free, timed passes for Sept. 24 and 25 were distributed on the website and via a special phone service. By noon Saturday, passes over the following two weekends were sold out, too. Passes for later in the month and into October are still available.

Members of the public reported problems getting through on the phone and navigating the website to request the passes to the museum, located next to the Washington Monument on the Mall. A Smithsonian spokeswoman said demand was high, but the services were both operating.

President Obama is expected to attend the museum's dedication at 10 a.m. Sept. 24. The museum will open to the public from 1 to 6 p.m. that day and from 10 a.m. to midnight Sunday.

The timed passes, being used to control crowds and entrance wait times, designate a 15-minute window for entry into the newest Smithsonian museum. Once inside, visitors can stay as long as they wish.

Because of the expected crowds, the timed passes will be used indefinitely, officials said.

Tickets can be obtained through the website, nmaahc.si.edu, or by calling 800-514-3849 or 919-653-0443 between 9 a.m. and 8 p.m. Monday through Saturday and noon to 8 p.m. Sunday. There is a limit of six passes per request.