The investigators established that the fraudsters posed as Safaricom agents before picking on a target.
They then convince the victim to have them replace their till or agent number and in the process obtain their confidential details.
Using the details, they install a Safaricom app on their mobile phone and withdraw the money there before fleeing.
Arrested on Saturday were Evans Ngui Dorcas, 32, and Jackline Mwende, 24, who were trailed to Ngariama area where they were arrested and escorted to Itabua Police Station.
They were held for the weekend as detectives hunted down more accomplices.
The DCI cautioned MPesa operators and other businesspersons of numerous fraudsters roaming around them guised as agents of reputable companies.