Seoul, South Korea (CNN) -- The head of the company that operated a passenger ferry that sank off South Korea last month killing more than 260 people was arrested Thursday, a senior prosecutor in the investigation told CNN.
Kim Han-sik, chief executive officer of Cheonghaejin Marine Company, is being charged with "causing death by negligence, as well as causing the capsizing of the ship in the line of duty," prosecutor Yang Joong-jin said.
Kim also faces a charge of violating the ship safety act, Yang said, in connection with allegations that excessive cargo a played a role in the April 16 sinking.
Investigators have said the cargo and the failure to tie it down properly was partially responsible for the sinking of the ferry Sewol, which was carrying 467 passengers and crew -- including more than 300 high school students on a field trip.
Investigators said they've indicted four employees of the ferry's owner in the last two weeks, including a senior executive Tuesday. Details about the charges weren't immediately available.
Authorities took aim at the cargo Tuesday, saying its weight was more than double the ship's limit. The cargo wasn't tied properly -- and the loosely tied goods helped cause the ship to capsize, Yang has said.
Investigators had been probing the possibility the ship overturned because cargo shifted and forced the ship off balance.
At least 269 people died in the disaster, which happened while the ferry was traveling from Incheon to the resort island of Jeju, off South Korea's southwestern coast. Thirty-five people still are unaccounted for, according to the country's coast guard.
News of Kim's arrest comes nearly a week after South Korean authorities searched Cheonghaejin Marine's offices as part of a criminal investigation.
This trip wasn't the first time the ferry had excess cargo, a joint investigation team told reporters Tuesday.
Since the Sewol began the Incheon-Jeju route in March 2013, the ferry carried excess cargo 139 times, investigators said.
Cheonghaejin Marine earned an extra 62 million South Korean won ($62,000) for the excess cargo on the April 16 voyage, and nearly 3 billion South Korean won ($2.9 million) in extra profit for all of the excess cargo that the ferry carried since March 2013, investigators said.