Police arrested seven people for negligence related to a petrochemical spill 10 days ago in southern China’s Fujian province that injured 53 people and dumped tons of pollution into the sea.

Those arrested include three employees of Fujian Donggang Petrochemical Co. and four workers on a chemical tanker. They were detained for the alleged crime of negligently causing a serious accident, according to the city government of Quanzhou, where the accident occurred. The penalty could be as much as 15 years in prison.

The spill released nearly seven metric tons of C9 aromatic hydrocarbon — a substance frequently used as a solvent in paint and rubber products —into the water at a petrochemical terminal in Quanzhou.

Fifty-three people received medical attention for suspected exposure to the leaked hydrocarbons. Two of them were still hospitalized Wednesday, the government said.

The leak occurred while the material was being transferred through an aging hose pipe onto a Donggang Petrochemical tanker at the terminal, according to an official statement last week.

Floating oil in the affected waters has been mainly cleaned up, the Quanzhou government said, although local residents voice lingering concerns over its effects on the fishery business.