The principal M N Krishnan Kutty, who was among the seven persons booked on June 10, was not arrested on Wednesday as he was ill, police said.
Kutty was arrested last night and later granted bail, they said. The six persons arrested on June 11 included four students, lecturer and staff Editor Gopi and magazine designer Rajeev.
Police had also raided the polytechnic on June 11 and confiscated 392 copies of the magazine, a computer and hard discs of the designers of the magazine.
On Jun 10, they were booked by police and cases registered against them for offences under Indian Penal Code (IPC), including concealing design to commit offence, wantonly giving provocation, punishment for defamation and printing matter known to be defamatory.
The campus magazine for 2013-14 was released recently and one of its pages titled 'negative faces' featured a photograph of Modi. Others in the collage included sandalwood smuggler Veerappan, LTTE supremo V Prabhakaran, Adolf Hitler, Al-Qaeda chief Laden and George W Bush, police said.