A South Korean passenger ship carrying more than 470 people, including many high school students, is sinking off the country’s southern coast Wednesday after sending a distress call, officials said. There are no immediate reports of casualties.

The ferry with 476 people, including 325 high school students, was sailing to the southern island of Jeju when it sent a distress call Wednesday morning as it began leaning to one side, according to the Ministry of Security and Public Administration.

A total of 18 helicopters and 34 rescue boats were sent to the area, and 110 people were rescued early in the response, the Associated Press reported, citing ministry officials.

Government officials said they had no further details.

Photos from South Korean media showed the ship on its side as rescue vessels were nearby.

YTN TV footage showed the vessel, named “Sewol” or “time and tide” in Korean, mostly submerged on its side in calm waters near the shore off Jindo island, northwest of Jeju, Bloomberg News reported. The ship may have hit rocks in heavy fog, the broadcaster said, citing a South Korean government official.

The vessel is owned and operated by Chonghaejin Marine Co., a company official told Bloomberg by phone, asking not to be named, citing internal policy.

The 6,825-ton ferry can carry as many as 921 passengers and 130 vehicles traveling between Incheon and Jeju island, which is popular among honeymooners and holiday-makers.