Raids were part of TVP's biggest-ever investigation into drugs, modern slavery and human trafficking.
The two car washes were in Whaddon Way, Bletchley and one at Peartree Bridge.
15 people have now been arrested as part of an investigation into an organised crime group that has been operating within Milton Keynes.
The group is believed to be responsible for large quantities of class A drugs being brought in from London and then being dealt on the streets of Milton Keynes.
The group were using the MK car washes as a front for criminal activity.
180 officers attended raids, executing 20 warrants. 25 people have been discovered and are now being safeguarded.
Officers seized a large quantity of cocaine, cannabis and also thousands of pounds worth of cash and a Mercedes ML 250 from across 20 residential addresses.