Two Administration Police officers were on Thursday arrested for providing security for three people posing as officials of the National Environment Management Authority (Nema).
The five were apprehended in Lunga Lunga, Kwale County, on allegations of extorting money from unsuspecting residents.
The police report stated that they had also been collecting money from the operators of buses that ply the Mombasa-Lunga Lunga Highway.
Lunga Lunga is the constituency that borders Tanzania.
The AP officers were identified as Captain Benson Njoroge, who is Kiamumbi AP Post, and Constable Margaret Maina who is based at Kamiti Corner. Both stations are in Kiambu County.
The three suspects said to have been posing as Nema officials were identified as Duncan Njogu, Grace Wambui and Purity Mumbi.
The Directorate of Criminal Investigations said the vehicle the suspects used - a Nissan Tiida - was impounded. Mr Njogu was the driver.
The DCI said, "The five suspects had already received money from more than three complainants, including Sh25,000 sent to Duncan Njogu's mobile phone. Kwale Nema officers confirmed that the suspects were not their officers."
Kwale County Police Commander Tom Odero said detectives believed the suspects began by defrauding motorists who used the highway.
"We believe Lunga lunga was their end-point. We are working with colleagues from elsewhere to establish where they started this operation," Mr Odero told the Nation.
The suspects were taken to Lunga Lunga Lunga Police Station and will be arraigned in a Kwale court on Friday.
Mr Odero said one escaped but that police launched a search.