A man has been arrested on suspicion of entering a school campus while wearing a female uniform.

Police on Tuesday said a man broke into a secondary school in Cheung Sha Wan on Monday, and fled after being spotted.

"Our investigation shows that the man snuck in during the school's lunch time, and left immediately after a teacher saw him," inspector Wong Yuen-yan said.

She said they arrested the suspect, 36, in a Yuen Long car park on Monday night on suspicion of loitering, after checking security camera footage.

Wong said the force is looking into why the man, who claimed to be a medical worker, allegedly broke into the school.