DALLAS (AP) — Nearly 20 Houston-area residents say test results have detected toxic substances in soil, water and ash samples taken miles from a chemical plant that flooded during Hurricane Harvey, caught fire and partially exploded.

The findings were disclosed Monday afternoon in a letter the residents’ lawyers mailed to the chief executive of the plant’s owner, Arkema Inc., and several regulatory agencies, giving notice that they planned to sue.

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The letter accuses Arkema of violating multiple environmental protection laws because of unauthorized chemical spills and releases that happened when the company failed to properly store and contain its organic peroxides before and after six feet of water overwhelmed the facility.

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Arkema representatives could not immediately be reached Monday evening. The company has refused to say which chemicals were released during the fire and has repeatedly declined to discuss how large its inventory quantities were prior to the incident.

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