(CNN) More than 300 people were injured after a wooden platform collapsed at a music festival in Spain late Sunday night, according to the local police and a spokesperson for Xunta Galicia's health department.

One person suffered serious injuries, the department spokesperson told CNN on Monday, adding that of the 316 injured, nine people remained hospitalized.

The incident happened at around midnight during an outdoor concert on the final evening of O Marisquiño, a three-day culture and sports event in Vigo on Spain's northwest coast, a spokesman for the city's police department said.

Dozens of people were trapped or fell into the sea after the platform, which was part of the existing harbor structure, collapsed.

It is currently unclear why the platform, seen on the left, collapsed during the concert Sunday night.

Read More