Two children who attended a summer day camp in Portland have been diagnosed with an antibiotic-resistant skin infection commonly known as MRSA, city officials said Tuesday.

City Hall spokeswoman Jessica Grondin said one child was hospitalized but has since been released.

The children attended a day camp based at Riverton Community Center, but it’s not known exactly where they contracted MRSA, which stands for methicillin-resistant Staphylococcus aureus.

“I don’t think it’s fair at all to say the building was affected. Rather two kids who go to the same Rec summer camp reported contracting this,” Grondin said in an email. “There is no indication or findings that it came from the building at all.”

Custodial staff spent Monday night and all day Tuesday cleaning and disinfecting common areas that may have been touched by the children.

Grondin said there is minimal danger to the public, adding that “MRSA is very common now.”

She said staff from the city’s Recreation Division took all the necessary steps, notifying the Maine Center for Disease Control & Prevention.

Attempts to reach the Maine CDC were unsuccessful Tuesday, but Dr. Dora Anne Mills, the former director of the Maine CDC who is now vice president of clinical affairs at the University of New England, said there seems to be little cause for public concern.

“It’s certainly nothing I would be too alarmed about,” Mills said Tuesday night. “I would still send my kids to camp there.”

Mills said over the years outbreaks of MRSA have become much more common because of the overuse of antibiotics by physicians. Summer is prime time for skin infections because children tend to get more cuts and scrapes from being outside more. Parents should take extra care to make sure those cuts and bruises are tended to.

“Good skin hygiene is very important,” she said.

Parents of campers received a letter, dated Monday, informing them of the situation. It was signed by Sally L. DeLuca, director of the city’s Department of Parks, Recreation and Facilities.

“While we cannot draw any conclusions of where the children contracted MRSA, out of an abundance of caution we will be cleaning and disinfecting community surfaces over the next two days,” DeLuca wrote. “Children will not return to their respective areas until this cleaning takes place.”

In an email to the Portland Press Herald, DeLuca said the older children in the summer day camp program participated in an all-day field trip to Popham Beach State Park on Tuesday, while the younger ones were based at a different community center and “did playground hopping all afternoon.”

“This gave custodial staff a chance to clean and disinfect Monday night and all day today,” DeLuca said Tuesday. “We have a few classrooms left to do on the school side tomorrow, so children will be kept away from this area. Older kids will be at Aquaboggan all day tomorrow.”

According to the Recreation Division’s website, the city operates a summer adventure camp for grades K-4 at the Riverton Community Center. Week 6 of the day camp runs from July 31 to Aug. 4 and features a trip to Popham Beach.

DeLuca said that “MRSA skin infections often look like a spider bite, boil, abscess or an infected hair follicle. A skin infection of this kind could spread into more serious illness if not treated.”

She urged parents to contact their primary care physician if a family member displays symptoms.

MRSA has become a serious threat to human health. In 2011 it was responsible for more than 80,000 invasive infections and more than 11,000 deaths in the United States, according to federal statistics.

According to the Maine CDC website, MRSA is a type of staph bacterium that is resistant to certain antibiotics such as methicillin, oxacillin, penicillin and amoxicilin.

Most infections appear on the skin and are considered noninvasive. Staph infections, the Maine CDC says, are spread by direct skin-to-skin contact with another person. They can also be spread through contact with items that have been touched by people with staph.

Some examples may include: shaking hands, wrestling, sharing towels, or sharing athletic equipment. Fluid from staph infections, especially boils, is particularly infectious. Symptoms manifest themselves in infections that look like a pimple or boil and which can be red, swollen, painful, or have pus.

The Maine CDC says that staph bacteria are one of the most common causes of skin infection in the United States. Most MRSA infections occur among patients in hospitals or health care settings, but the agency said infections are becoming more common in community settings.

Staff Writer Noel K. Gallagher contributed to this report.