SANTIAGO (Reuters) - Chile’s environmental regulator expanded its investigation into a gas poisoning incident in coastal town Quintero, bringing charges of non-compliance with environmental agreements on Monday against a gas plant.

The environmental inspectorate (SMA) said Gasmar, a company that imports and sells liquefied petroleum gas and is part-owned by Chilean industrial conglomerate Copec, has 10 days to present a compliance plan or appeal the accusation that it failed to adhere to agreed levels of residual gas flaring from its chimneys.

The charge against Gasmar comes on the heels of stricter monitoring by SMA following a gas poisoning incident in August in which hundreds of people showed symptoms of gas inhalation poisoning, prompting ongoing protests over the government’s handling of the issue.

Within days, the SMA ordered the suspension of some operations by the state-owned energy company ENAP[ENAP.UL], also in the Quintero industrial zone, about 90 miles northeast of Santiago. The company has denied responsibility for the incident.

The SMA said in a statement on Monday that its audit of Gasmar’s operations had not yet detected any pollution or harm caused to people living nearby. However, it called the charge against Gasmar “serious” and said it was brought because the company failed to mitigate its potentially adverse environmental impact.

Quintero has had several pollution incidents in the past, including gas and oil leaks, leading to investigations and fines against companies for non-compliance with environmental obligations.

The SMA has admitted it struggles to supervise the operations of the 15 large-scale industrial plants based in the area.

Environment Minister Carolina Schmidt told local television station Canal 13 over the weekend that ENAP was not the only company responsible for polluting the area. She said the government had asked state miner Codelco and AES Gener, an electricity generation firm, to provide information about their emissions on Sept. 4 when another environmental incident left 20 people ill.