Mass stabbing at US high school

As many as 20 students have been injured in a mass stabbing at a high school in the US state of Pennsylvania, authorities have said.
One suspect believed to be a student is in custody at Franklin Regional High School in a suburb of Pittsburgh, a local affiliate of ABC News reports.
The wounded, at least four with significant injuries, range in age from 14-17 and have been taken to hospital.
The school was locked down as police searched the premises.
"A critical incident has occurred at the high school. All elementary schools are cancelled, the middle school and high school students are secure," school officials wrote in a bulletin following the incident Wednesday morning.
Four students are seriously injured, while other students were said to have suffered scrapes and cuts in the mayhem that ensued following the attack, emergency management spokesman Dan Stevens told US media, according to a news agency.