A secondary school said on Friday it had appointed its vice-principal to run the school's affairs while its principal is under police investigation over a charity that helps students quit drugs.

The principal of United Christian College, Simon Lau, is reportedly one of four directors of the non-profit Zheng Sheng Association who were arrested on Thursday on suspicion of conspiring to defraud donors of HK$50 million.

"The school has learnt that Principal Simon Lau is under investigation in connection with the Zheng Sheng Association," said a statement from the governing body of United Christian College.

The school stressed that it had no connection with the association and that Lau's involvement was in his own capacity.

It said it had set up an emergency group under the instruction of the Education Bureau to ensure the smooth running of the school and to minimise any possible impact on student learning and school management.