DENVER » Denver police said there were no major problems as marijuana celebrations continued for a second day on Sunday, but police tweeted a reminder that while recreational use of marijuana is legal in Colorado, people still can’t use it in public.

Police spokeswoman Raquel Lopez said there was no estimate on the number of people who turned out on Saturday and Sunday, including many tourists who flocked to Colorado to take advantage of legal marijuana.

"We’d prefer not to be buzzkills this 4/20 weekend. Consume responsibly, and designate a sober driver now," police tweeted on Sunday.

On Saturday, police issued about 60 citations. Police said most were for public consumption. No information was available on any arrests on Sunday.

"It certainly seems to be going OK," Lopez said Sunday.

The law against public consumption is widely flouted, especially around the 4/20 celebrations. Celebrations were held over the weekend near the Denver City and County Building, but police said no one had a permit in Denver for Monday, the unofficial stoner holiday of 4/20. However, a number of people were still expected to show up, and Lopez said police will issue citations at their discretion.

The origins of the number 420 as a code for marijuana are murky. Fans of the drug have long marked April 20 as a day to enjoy pot and call for increased legal access to it.

A small plane flew over the crowd with a banner urging people to grow their own marijuana.

Meanwhile, the University of Colorado will keep the Boulder campus open to the public on pot day this year, the first time in three years since university officials tried to snuff out the once-massive marijuana smoke-out on campus.

Chancellor Phil DiStefano said he felt that a lack of activity on April 20 in the past three years made it possible to keep the campus open this year.

The university said marking 4/20 is contrary to its mission of research, teaching and learning.