Kenya's long, porous border with Uganda remains the biggest challenge in the fight against smuggling of plastic bags, the National Environment Management Authority (Nema) has said.
The environmental watchdog has raised the alarm over rising cases of the crime, noting Uganda has not banned the products.
Nema's Busia County Director Edward Menza said the porous border has remained a major route for smuggling counterfeit and illegal goods through Sofia, Marachi and Mayenje estates.
"The state of our border in Busia allows citizens of the two countries to cross over with ease. This has in turn derailed efforts to effect the ban in the region," he said.
Mr Menza said criminals no longer labour to sneak bales of plastic bags into Kenya.
They do so in small quantities to beat security checks, he said at Busia Police Station on Tuesday after an operation to nab plastic bag users.
But the authority has vowed to ensure the law that banned use of plastic bags is fully enforced.
Six people were arrested during the crackdown in Busia town and its environs, after they were caught using the bags to package vegetables, sugar and fruits.
"Since we started the raids last week, a total of 45 suspects have been arrested in Matayos, Nambale, Butula, Teso North and Budalang'i. They had between 50 and 1,000 flat clear bags," Mr Menza said, adding the larger bags seem to have been phased out.
"Those we have arrested supply the bags in small quantities to traders who order them for daily use. We suspect some traders have these bags stored in their houses," he added.
The official reported, however, that since the ban was effected in 2018, use has reduced drastically.
Mr Menza said one person was arrested for extortion by pretending to be a Nema official.
"Two suspects who had been closely following our movements were apprehended last week by members of the public and taken to Busia Police Station," he added.
Mr Menza said an accomplice who was not arrested had been visiting petrol stations in Busia with fake affluent compliance certificates.
He added, "We have been informed of a case in Port Victoria in Budalang'i that we are following up on."
In Kisumu, eight arrests have been made in the last one week.
The county's Nema director Tom Togo said the crackdown targeted traders at open air markets, kiosks and petrol stations, as well as hawkers.
"Those in possession of polythene bags are hiding and some have even closed their businesses, which makes arrests difficult," Mr Togo said, adding they were warned of the crackdown.
The use, manufacture and importation of all plastic bags for commercial and household packaging was banned in Kenya effective August 28, 2017.
Those found guilty of using them risk a two-year jail term or a fine of between Sh2 million and Sh4 million.
According to Nema, the polythene papers contribute nine percent of total waste and cause more than 90 percent of environmental degradation.
Amid crackdowns, Nema has been criticised for failing to take acting against people found with plastic bags.
Mr Michael Nyaguti, Magnam Environmental Network director, said the authority was "full of big talk with no action".
"The authority is a barking dog that never bites. They have a responsibility they are not undertaking. Many traders in Kisumu have polythene bags and are using them freely," said Mr Nyaguti.
He asked Nema to quickly arrest and prosecute culprits as a lesson to others.