State authorities say they’ve seen a jump in the number of complaints about tattoo parties and tattooing of minors, prompting them to issue a public warning that such practices are illegal in Maine.

The Maine Center for Disease Control’s Health Inspection program has posted a notification about the issue on its website. The state says the number of tattoo complaints — most of which were connected to tattoo parties — increased from 13 in 2010 to 31 in 2011.

“We’ve tried really hard to get the word out that it (private parties) is not a safe practice,” said Lisa Roy, who serves as program manager for the state’s Health Inspection Program. “In order to place a tattoo on another human being, you have to be licensed by the state.”

Roy said a state-licensed tattoo practitioner ensures that the artist has received proper safety training, operates a sanitary facility, and makes sure that needles and medical waste are disposed of properly. Roy said state inspectors, working in conjunction with local police departments, have raided parties on occasion, though no raids were conducted during 2011.

Roy said tattoo parties typically are advertised on social media websites such as Facebook and Twitter, which are the online sites police use to find parties.

That’s how a tattoo party came to the attention of Trooper Jeremy Forbes, a 16-year veteran of the Maine State Police, two years ago. Forbes said state police received an anonymous complaint in August 2010 from a person who had seen a tattoo party advertised on Facebook.

Forbes teamed up with a state health inspector. When they arrived at the party — a home in the York County town of Lebanon — they peeked in a window to see what was going on.

Forbes said he did not have a warrant, but the homeowner let them into the residence after they knocked on the door.

“They were very helpful,” he recalled. “The homeowner wasn’t aware that a party was illegal.”

Of the dozen or so party guests, only two had received tattoos.

The person who had been tattooing party guests was not there, but he returned a short while later.

When Forbes questioned the man, a 21-year-old Saco resident, he said he was unaware that he was breaking Maine law.

Forbes issued him a summons for illegal, unlicensed tattooing — a Class E criminal offense that is subject to a fine of between $50 and $500 or up to six months in prison.

Though raids are uncommon — Forbes has been to only one in his career — he said law enforcement takes such complaints seriously because of the health risks involved with getting a tattoo in a private residence.

Receiving a tattoo from an unlicensed tattoo artist increases the risk of skin infection and transmission of diseases such as HIV, Hepatitis B, and Hepatitis C, the state warns.

“If it’s reported to us, we have an obligation to take it seriously,” Forbes added.

Another common complaint received by the state concerns the tattooing of minors. State law prohibits tattoos being placed on anyone younger than 18.

Tattoo artists such as Chad Chase, the owner of Venom Ink in Sanford, are licensed by the state.

Chase said tattoo parties in Maine and across the country have gone on for years.

Chase frowns on home parties, a form of unlicensed competition. He said they often feature an inexperienced tattoo artist who may produce poor results in an unhealthy setting.

“We don’t support parties at all,” Chase said. “We go out of our way to provide a safe setting.”

Tattoo prices at Venom Ink can vary widely, from a low of $80 to as much as $1,000. A tattoo at a private party might cost a 12-pack of beer or a $20 bill, he said.

Chase said party tattooers often buy materials on eBay before advertising a party on craigslist or Facebook.

“Seek out a real artist and check out their portfolio first,” Chase advised. “You may end up having a lot of regrets. Quality can be pretty low at a party. You get what you pay for.”

Roy, the state program manager, said there are 125 licensed tattoo practitioners operating in Maine.