Maritime police search for missing passengers in front of the South Korean ferry "Sewol" which sank near the island of Jindo on Wednesday. Reuters

Update as of 1 a.m. EDT: The death toll in the ferry sinking has risen to 169, CNN reported Thursday afternoon local time, citing prosecutors conducting a criminal investigation of the disaster.

South Korean rescue operation authorities said Thursday that the death toll from the April 16 sinking of the Sewol ferry had climbed to 162, leaving 140 passengers missing, CNN reported. Rescuers have not found a single survivor since 174 people were rescued the day the ship sank one week ago.

On Wednesday, investigators searched the offices of Cheonghaejin Marine Co., the company that owns the Sewol, expanding an investigation that has already led to the arrest of 11 crew members, the news site said. According to the Yonhap News Agency, the offices of 20 organizations affiliated with Cheonghaejin Marine as well as the home of Yoo Byung-eun, a billionaire whose family apparently oversees the company, were also searched.

Yoo, known in South Korea as a "millionaire with no face" considering he's seldom in public, apparently has an artistic alter ego -- Ahae -- as a photographer who has won worldwide recognition, a number of South Korean newspapers have reported. Yoo's website appears to show him taking photos, while he face cannot be seen, CNN reported.

Yoo and two sons control the shipping company that operated the ferry. Days after the Sewol sank, the company sent out its president to apologize, but not Yoo.

In 1987, Yoo was was a religious cult leader, according to CNN. The news site wrote that more than 30 people from his group were discovered dead, "bound and gagged in a factory outside of Seoul. Officials investigated the incident as a mass murder-suicide, but found no evidence tying the event to Yoo."

The Sewol sank April 16 during a routine trip from Incheon to the resort island of Jeju. Among its 476 passengers and crew were more than 300 high school students on a field trip.

The Sewol's captain, Lee Joon-seok, and other crew members have been criticized for failing to evacuate the ship quickly and for giving orders for passengers to remain where they were, CNN reported. Lee has said he was worried about the cold water, strong currents and lack of rescue vessels.

Authorities still did not know what caused the incident. The ship wasn't apparently overloaded, according to figures provided by the company and the South Korean coast guard. However, coast guard officials said investigators won't know for sure how much cargo the Sewol was carrying until it's salvaged.