It is understood that person had since made it known to police that they had happened to walk into the toilet block at that time.
The police spokesperson said the toilet block had been cleaned by 7am that morning and they received the report of the blood around 1.25pm, indicating a time window for the incident to have occured.
"Police are still working to ascertain the circumstances of how [the blood] came to be there," the spokesperson said.
An appeal for information has been launched, with the public encouraged to get in touch with police as soon as possible if they have any information about what happened.
Anyone who has information that could help is asked to contact Detective Steve Yates by calling the police non-emergency number 105.
Levin Police Station can be reached on 06 366 0500.
If you or someone you know needs immediate assistance call emergency services on 111.