Kibos Sugar and Allied Company in Kisumu has been shut over air pollution.
Acting National Environment Management Authority director-general Mamo Mamo said on Friday that the company had failed to comply with air regulations despite being given 30 days to comply.
Mamo said in a letter dated March 5 that factories must maintain 50 micrometres of what they emit into the atmosphere.
Kibos has been emitting 245 micrometres of pollutants, five times more than the national standards.
The company will re-open only after installing an effective air pollution control system and to the satisfaction of Nema.
He said the company must adhere to emission reduction measures as set out in part (IV) of the 5tg schedule of the Air Quality Regulation 2014.
"Further note that section 143(a) provides that any person who fails, neglects or refuse to comply with an environmental restoration order under this Act commits an offence and shall, on conviction, be liable to imprisonment for a term not exceeding 12 months or a fine of Sh500,000 or both," the letter said.
The letter is copied to among others Kisumu county commissioner.
Recently, the company successfully appealed against an environment court's order to close it for polluting rivers.