Prosecutors entered a church retreat Wednesday to find and detain the de facto owner of a sunken ferry Sewol who has refused to appear for questioning over corruption allegations.

A group of some 70 prosecutors and investigators, armed with court-issued warrants, entered the premise belonging to the Evangelical Baptist Church, where Yoo Byung-eun was suspected of hiding, around noon in Anseong, just south of Seoul. Yoo remains an influential founding member of the religious sect.

Yoo -- an entrepreneur, artist, ex-convict and religious figure -- is believed to own Chonghaejin Marine Co., which operated the ferry Sewol that sank off the southwest coast last month, leaving more than 300 people dead or missing.

The prosecution suspects that corruption by Yoo, whose two sons own stakes in the firm through various subsidiaries, resulted in lax safety practices, such as cargo overloading, and created an environment that ultimately led to the April 16 sinking.

On Tuesday, prosecutors investigating the case raised the possibility that Yoo and his eldest son, Dae-kyun, had already slipped out of the retreat and could be hiding at the residence of one of the worshipers in Seoul.

"The search is progressing well with the active cooperation of the retreat, but there has been no report yet that the father and the son have been found," Kim Hoe-jong, a senior prosecutor investigating the case, said in a press briefing.

Nearly 100 worshipers built a blockade in front of the huge retreat, nestled between mountains near Anseong, 77 kilometers from Seoul, but did not resist or try to stop the investigators from entering the premises.

They have been staging a sit-in at the gate, arguing that the church has nothing to do with the allegations raised by the prosecution and that the ongoing investigation is religious persecution.

The prosecution said a total of 1,200 police officers, in riot gear, have been deployed around the sprawling religious compound to prevent a possible clash between prosecutors and members of the church.

"We have repeatedly told that the investigation has nothing to do with religious matter but is about personal corruptions surrounding Chonghaejin Marine and other companies," Kim said.

The church was established by Yoo's father-in-law, Kwon Sin-chan, in the 1960s. It is widely considered a cult, with its some 20,000 followers, including most of the senior officials of Chonghaejin and its affiliates.

The church, under a different name, was also allegedly involved in a 1987 high-profile mass suicide-murder. More than 30 people from the group were found dead, bound and gagged in a factory outside of Seoul. Investigators, however, found no evidence tying the event to Yoo.

The raid was also part of the efforts to obtain related documents and other evidence revealing the whereabouts of the Yoo family, prosecutors added. 

Yoo is facing a host of corruption charges, including embezzling company funds, dereliction of duty, tax evasion and bribery, according to the prosecutors.

The prosecution further alleged that the Yoo family established three paper companies to create slush funds and illegally transfer money abroad by embezzling corporate funds while failing to fulfill the duty of properly managing the companies.

Prosecutors have tried to determine whether the family illegally used the ferry operator and other businesses to accumulate a fortune, but the family members have ignored their summonses.

Yoo Dae-kyun has already been put on the most wanted list for continuously disobeying the summonses.

Prosecutors have also sought arrest warrants for Yoo's second son, Hyuk-ki, and eldest daughter, Som-na, both currently staying abroad, as they have also repeatedly refused to respond to prosecution summons.

Also, the foreign ministry said it has ordered both Hyuk-ki and Som-na to return their passports at the request of prosecutors. (Yonhap)