Police on Wednesday raided the compound of a religious group connected to fugitive billionaire Yoo Byung-eun, wanted in the South Korea Sewol ferry disaster which cost the lives of 292 people, many of them young students.
Reports by the BBC say the police, numbering around 6,000, raided the sprawling compound in Anseong, South Korea, believed to be hiding Yoo, 73, and evidence about his activities.
The compound is owned and run by a Christian group called the Evangelical Baptist Church, founded by Yoo's father and widely regarded by critics as a cult, according to reporting by CBS.
Earlier in the week, South Korean President Park Geun-Hye had urged police and prosecutors to increase efforts in the search for Yoo.
It is still unclear if the reclusive billionaire was found at the compound, but several church members were detained after being accused of providing Yoo shelter or helping him escape.
Most experts believe Yoo is still in hiding in South Korea, after one of his associates made a failed attempt to seek asylum at an embassy in Seoul on his behalf.
On May 27, Yoo's daughter, Yoo Som-Na, was arrested in Paris, France, after an Interpol Red Notice, against her and a brother.
The daughter, 47, is held on embezzlement charges, and according to Yonhap News Agency is expected to be extradited to South Korea. On Wednesday, a French court rejected the daughter's request for bail.
The two children are believed to be involved in or controlling Chonghaejin Marine Co., the company that owned and operated the capsized ferry.
On Tuesday, 15 crew members from the Sewol ferry disaster went to trial. The ferry captain, Lee Joon-seok, 69, and three others face the most serious charges of "homicide through wilful negligence."
In 1987 Yoo's church was suspected of involvement in a suicide pact that left 32 dead in a factory attic near Seoul, after financial transactions from one of the dead showed funds had been funneled to him.
Due to lack of evidence the charges against Yoo and the church were dropped, but Yoo later spent four years in prison convicted on a separate fraud charge.
The reward for information leading to Yoo's arrest has been raised by South Korean authorities to close to $500,000, or 500 million Korean Won.