Thirty-one die-hard Grateful Dead fans, known as Deadheads, were arrested at the 1960s-era rock 'n' roll band's Long Beach Arena opening concert, but police said there were no major problems. Thirteen adults and 18 juveniles were booked for being under the influence of drugs or alcohol, Lt. Rod Mickelson said. Two people who had ingested hallucinogenics were treated at Pacific Hospital in Long Beach and released, Mickelson said. Long Beach police said two drugs of choice were LSD and magic mushrooms (psilocybin), which were popular in the 1960s but are rarely seen at today's rock concerts. Several hundred Deadheads, many of whom follow the Grateful Dead from city to city, turned a huge arena parking lot this weekend into an asphalt campground reminiscent of scenes two decades ago, selling tie-dyed T-shirts, peace bumper stickers and buttons. The band is in Long Beach for a three-day stint.