Two South Korean college students who were in Cambodia on a volunteer trip have died of unknown causes. 

Konyang University said on Thursday that two of its juniors who were in Phnom Penh died while being treated at a local hospital for stomach pain. 

According to the Daejeon-based college, both initially visited the hospital on Tuesday complaining of a stomach ache, but were discharged later in the day as their conditions improved. 

The following day, they were taken back to the hospital after symptoms returned. One died Wednesday afternoon and the other on Thursday morning. 

The exact cause of death remains unknown. Other members from the school are known to have no significant health problems. 

Nineteen faculty members and students from the college left for Cambodia on Sunday. They were due to return next Wednesday, but will likely cut the trip short. The college also plans to send an emergency team to Cambodia.