Of the 29 held, 11 have been charged.
"Ticket touting is illegal and is a clear exploitation of those who genuinely wish to experience the Games first-hand," said the officer in charge of a crackdown on illegal ticket re-sellers.
"We have been, and will continue to, seek out and take robust action against anybody who tries to cash in on the 2012 Games in this way," Detective Superintendent Nick Downing said in a statement over the weekend.
Many Britons have been frustrated by their inability to buy tickets for the Games, and exasperated at television images of rows of empty seats at some venues.
But police warned against buying from touts.
"If you do, you are likely to find yourself paying over the odds for them, while at the same time fuelling criminality," Downing said.