Hungarian prosecutors on Thursday have officially levied charges against the captain of a river cruise ship involved in a deadly boat sinking in May that killed 25 South Korean tourists.

According to local media, the 64-year-old Ukrainian captain of the Viking Sigyn, identified as Yuriy C., was charged by prosecutors in Budapest with negligent endangerment of water traffic leading to a fatal mass catastrophe.

On the Danube River in Budapest May 29, the cruise ship struck and sank the Hableany, a smaller tourist boat with 35 people on board. 

Twenty-five South Koreans and two Hungarian crew members were killed in the nighttime crash, while seven South Koreans survived. One South Korean tourist remains unaccounted for. 

Hungarian prosecutors said that Yuriy C. failed to pay sufficient attention and did not focus on steering the ship for several minutes. They said the captain also failed to keep a safe distance and did not send the necessary radio and sound signals when being overtaken by another boat.

Prosecutors reportedly said Yuriy C. could face eleven years in prison if convicted, but added that they plan to seek nine years if the captain pleads guilty at a preliminary hearing and foregoes his right to a trial.