(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.
Vigo festival: Hundreds injured in Spain after platform collapses
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.
In a statement Monday, the organizers of the festival said that they "deeply regret the accident" and that the area in question has been sealed off to allow experts to determine the cause of the collapse.
It added that the O Marisquiño concerts "met the security conditions required by legislation" and that organizers were available to speak with authorities as needed.
Soon after the incident, pictures of the caved-in walkway began appearing on social media.
Angel Poutas, 19, was at the concert and filmed the immediate aftermath of the collapse.
He told CNN that the area had become more and more crowded as Rels B, a rap artist, took to the stage shortly before midnight.
"Suddenly we heard a super strong crack, and I felt the ground disappear under my feet, and everyone fell into the hole in the middle," Poutas said. "I only lost my sweater into the sea, but people to my right started falling by, rolling over me. People screamed, shouted. I asked for help to find people who fell down into the hole by the sea, including a friend of mine, who is in the emergency room."
He said that he helped a girl with a broken knee and a boy who couldn't walk on his ankle.
Rels B tweeted his support for the victims, wishing "strength to the wounded."
According to Vigo's mayor, Abel Caballero, firefighters, local and national police and civil guard officers were all active on the scene overnight.
As false rumors of fatalities quickly spread across social media, authorities urged users not to share unverified information and to wait instead for confirmed reports from the police.