The National Truth and Reconciliation Commission said Thursday that at least 150 fishers who returned home from a North Korean abduction more than 50 years ago were abused by the South Korean police during a series of interrogations.

In a preliminary report released Thursday, the commission said that the 150 fishers were detained without a warrant and interrogated by the police after they were sent back to the country on May 28, 1969.

The commission made the determination after looking into a total of 982 fishers who were returned after being abducted by North Korean authorities between 1965 and 1972. The investigation on the rest of the repatriated fishers, which began about a year ago, is still underway.

The commission said some of the fishers were followed by South Korean authorities for years over their suspected ties with North Korea. Their families were also watched, and suffered discrimination in employment and housing.

While many of the fishers were punished at the time for going over the Northern Limit Line, the maritime border between South Korea and North Korea, the commission said the criminal convictions were also likely a result of police violence.

The commission said court documents and other public records suggest they were forced to give a false confession. “It appears that the fishers were kidnapped by North Korean sea patrol authorities during normal fishing operations but forced to confess otherwise under torture,” it said in Thursday’s report.

The commission urged the South Korean investigative authorities to give a formal apology to the repatriated victims of abduction for unlawful detention, coerced confession and surveillance. The commission also recommended that the South Korean government take specific actions, such as a retrial, to help the victims recover.

In a separate report also released Thursday, the commission found that some of the victims of the “reformation” camps set up under Chun Doo-hwan, a former general who rose to power through a coup and ruled from 1980 to 1988, included minors.

One of those camps, operated from Sept. 20 to Oct. 18, 1980, exclusively admitted underage students, the commission said. Some 600 students from middle and high schools across the country were taken to the camp during this period.

According to the commission, the students were beaten and exploited as forced laborers at the camp. Then the police continued to surveil them after they were released. The police surveillance of former camp inmates was kept a secret from the public.

The commission believes that there are about 40,000 victims of the reformation camps while Chun was in power. At least 54 died while being held in such camps, according to the official count.