This undated file photo shows a dolphin at a dolphin show, provided by Hot Pink Dolphins. Yonhap

Police said Friday they have booked the staff of a theme park in the southern coastal city of Geoje in connection to the death of two dolphins that were thrown into a dolphin show despite being ill.

In February, two common bottlenose dolphins, July and Nova, were allegedly forced to take part in a dolphin show while undergoing treatment for an illness, then died three days apart at Geoje Sea World, 331 kilometers southeast of Seoul.

Police launched an investigation into the case after a marine environmental group, dubbed Hot Pink Dolphins, recently filed a complaint requesting they look into the deaths of the two dolphins.

After the incident, the local government, fisheries ministry and a basin environmental office conducted a joint inspection of the theme park, drawing the conclusion that they needed improvements in three criteria, including water temperature management, diet and hygiene.

The relevant law prohibits acts of negligence against animal or marine life, such as not giving food or water without proper reasons, or not taking appropriate measures when they are sick.

"Although there are some leads that raise suspicions that there was animal abuse, experts say the causality is not clear, which makes it difficult to take clear administrative measures," a local official said, adding they plan to get legal advice with records from the theme park indicating the causal order of the incident.

Police plan to look into whether there were any law violations based on the complaint. (Yonhap)