Oktoberfest 2014: 181st Celebration Gets Underway In Munich [PHOTOS]

Mayor Dieter Reiter opened Munich's two-week Oktoberfest beer festival Saturday, shouting "O'zapft is!" as he tapped the first keg. Persistent rain failed to dampen the spirits of festival-goers as thousands queued up at beer tents for the festival's 181st celebration.

Deutsche Welle reported some tents were so overcrowded, they had to be closed off to new arrivals -- even before the festival officially opened.

The beer is supplied by six breweries, all Bavarian, the Local.de reported. The region takes its beer seriously, introducing the Reinheitsgebot or purity law in 1516, considered the world's first consumer protection law. Then in 1539, it was decreed beer could be brewed only from September to April, but that law has gone by the boards.

Oktoberfest beer gets more alcohol than brews at other times of the year, the Local said. It's also lighter, sweeter and less carbonated.

Some 6 million of beer drinkers from around the world are expected in the Bavarian capital for the Oktoberfest, which runs to Oct. 5.