A new craze among teenagers in America known as 'sexting' has seen six high school teenagers from Pennsylvania facing child pornography charges after three teenage girls allegedly took nude or semi nude photos of themselves and shared them with classmates, via their mobile phones.

The 14 and 15 year old girls from Greensburg Salem High School face charges of manufacturing, disseminating or possessing child pornography. The boys, who are aged 16 and 17 face charges of session, according to WPXI-TV in Pittsburgh.

Police said that the pictures were discovered in October when teachers seized a phone from a male student and found a nude photo of a classmate on it. Police were called in and found more pictures on other phones.

Police Capt. George Seranko was quoted as saying that the first photograph was "a self portrait taken of a juvenile female taking pictures of her body, nude."

The school district issued a statement saying that the investigation turned up "no evidence of inappropriate activity on school grounds ... other than the violation of the electronic devices policy." The statement also said that school officials didn’t learn of the charges against the students until Monday.

Sanko indicated that authorities decided to press charges to send a strong message to other minors considering sending pictures of themselves.

"It's very dangerous," he said. "Once it's on a cell phone, that cell phone can be put on the Internet where everyone in the world can get access to that juvenile picture. You don't realize what you are doing until it's already done."

Patrick Artur, a Philadelphia defence attorney said that as there is no mandatory sentence under Pennsylvania’s child pornography law then it was unlikely that the students would be incarcerated. Convictions would have serious implications though including having to sign the sex offenders register for at least 10 years.

The National Campaign to Prevent Teen and Unplanned Pregnancy reported last month that a survey of 1,280 teens and young adults found that 20 percent of the teens said they had sent or posted nude or semi nude photos or videos of themselves. That number was slightly higher for teenage girls - 22 percent - vs. boys - 18 percent.