Thirty-one people were arrested in Mombasa on Monday for being in possession of plastic bags.
A vehicle ferrying the bags without a permit was also impounded.
Plastic bags were banned in Kenya with effect from August 28, with exceptions given for garbage bin liners and those used for packaging goods in industries.
The individuals were arrested in a crackdown by National Environment Management Authority and Mombasa County Inspectorate Department.
Nema enforcement officer Robert Orina said the team conducted the crackdown in Majengo Market and Tudor.
He said two of those arrested were suppliers of the banned bags.
“This is a breakthrough as we have had a successful crackdown. For the last two weeks Nema and the county government have been able to arrest traders [who are still] using the banned plastic bags,” Mr Orina said.
He said plastic carrier bags were a menace in Mombasa and caused pollution.
Some of the impounded plastic bags, he said, came from Uganda.
“We are following leads and tracking the dealers. We are going to work day and night to rid Mombasa and the entire country of plastic bags,” he said.
The suspects would be arraigned in court on Tuesday, officers said.
Mombasa Inspectorate director Mohamed Amir told the Nation the county would not tolerate the use of plastic bags and would work with the national government to enforce the ban.
He warned residents against using the banned bags.
“I want to ask the residents to help us secure our environment,” Mr Amir said.
He urged locals to use reusable bags to conserve the environment.
Nema earlier asked Kenyans to use bags made from paper, cloth and other biodegradable material.
On Monday, Nema and Mombasa County officials asked those still having plastic bags to surrender them to the authority or face arrest.