A Dutch company operating in South Portland has agreed to pay a fine to settle allegations that it violated federal rules for handling hazardous chemicals.

The company, Quick Plug N.A., created a soil-like medium used for growing seeds and small plants. It shut down in December, but a federal inspection before it closed found violations of hazardous chemical rules, including the company’s handling of toluene diisocyanate, the U.S. Environmental Protection Agency said.

EPA officials said Quick Plug broke the rules on handling the chemical, known as TDI, and failed to prepare and submit a risk management plan, which is used to help facilities handle hazardous chemicals safely.

Quick Plug agreed to pay a $137,294 penalty, the EPA said.

TDI is considered an extremely hazardous substance under the Clean Air Act. The EPA said it’s a possible carcinogen and can cause respiratory irritation or breathing problems if it is inhaled, and that people who have even minimal exposure to it can develop chronic asthma.

EPA inspectors said the problems they found included missing signs; fire hazards caused by the use of extension cords; a portable electric space heater in use inside the chemical storage area; improper storage of combustible wood pallets; lack of proper ventilation; failure to maintain equipment that was leaking TDI; and open drums of TDI-containing chemicals.