Bangalore: Two college students have been arrested in Kerala for celebrating their principal's impending retirement with a mock farewell involving crackers, sweets and a poster carrying a sarcastic "homage".

After chief minister Pinarayi Vijayan deemed the incident serious enough to condemn it in the Assembly and promise strong action, second-year students Sharat Damodaran (BSc mathematics) and M.P. Praveen (BA economics) surrendered before police on Thursday.

They were booked for negligence with explosives, defacing walls and causing public nuisance, which carry up to six months in jail and a Rs 1,000 fine, and given bail. A third accused, second-year BA economics student Mohammed Anees, is in hiding.

Principal P.V. Pushpaja, who retires only on May 31, has said in her police complaint that the trio are members of CPM student arm SFI. But the organisation said only Anees was a member and insisted he was innocent.

All three have been suspended by the Nehru Arts and Science College, a private institution at Kananghad in Kasargod, north Kerala.

The college authorities had held an advance farewell for the principal on March 27, where the accused allegedly burst crackers and distributed sweets.

Local media have published pictures of a handwritten poster that was put up and read: "Homage to the principal who has died in the hearts of the students.... A tragedy has ended and the campus is becoming free."

"I'm still finding it difficult to recover from the shock, (which I had to face) after spending my entire teaching career of 33 years in this college, from which I had graduated," Pushpaja told The Telegraph on Friday.

SFI state secretary M. Vijin told this newspaper that Anees was innocent.

"He is our Kasargod district committee member. His name has been dragged into this case," Vijin said. "No one blamed the SFI for a day. Our name cropped up only on the second day when the principal accused him before the media."

He added: "The SFI does not support humiliating any teacher. We condemn the incident."

Last May, the SFI had expelled three members for allegedly dragging out the chair of N.L. Beena, principal of Maharaja's College in Kochi, and setting fire to it.

In March 2016, a group of students at Victoria College in Palakkad had organised a symbolic funeral of their principal, T.N. Sarasu, decorating a notional grave with flowers. Three SFI members were arrested in the case.

The police have visited the Kasargod campus and collected remnants of the crackers burst on March 27.