ANSAN, Gyeonggi Province (Yonhap) -- Two in 10 students who survived last week's deadly ferry sinking require psychiatric treatment as they still suffer from serious mental stress and depression, a local hospital treating the students said Monday.

The Korea University Ansan Hospital in Ansan, 42 kilometers south of Seoul, is treating 81 survivors, including 74 students from Danwon High School in Ansan.

"We're considering sending about 20 percent of the patients to a psychiatric clinic with consent from themselves and their parents in the judgment that they require constant intervention (by the hospital)," said Cha Sang-hoon, chief of the hospital.

He referred to the students who were rescued from the ferry disaster that killed 61 passengers and left 238 others unaccounted for.

The students were on a school trip when the 6,825-ton ferry Sewol capsized and sank off the southwestern island of Jindo on its way to the southern resort island of Jeju on Wednesday.

Most of the surviving students have recovered from their initial anxiety and an inability to express their emotions, but some still suffer from serious mental stress and depression, according to the hospital.

The hospital said it will decide whether to allow the students who have recovered to be discharged after monitoring their condition for two to three more days.

With preparations under way to resume classes at the victims' school this week, the school authorities are considering special educational programs for the surviving students.

Right after the tragedy took place on Wednesday, Danwon High School decided to close the school for a week.

"In cooperation with relevant education entities, we are to organize special programs for the second-year students focusing on psychological treatment including one-on-one counseling services," said an official of the Gyeonggi Provincial Office of Education. "Such programs would be held at hospitals."

A total of 325 sophomores from Danwon were on a field trip to Jeju when the tragic incident took place. Of them, more than 200 students remained unaccounted for.

"For those in the third year, class will restart from Thursday, and for freshmen next Monday," the official said, adding that a special team of doctors, counselors and teachers will first attend to the students.