When they heard Maria's Spanish accent, they asked to see her papers, and searched her house for drugs. This creepy encounter is an example of what collaboration between the INS and local police looks like. For instance, the INS normally can't raid churches and schools, and police can't normally stop people based on their race. By collaborating, they can sidestep the rules. INS-police collaboration, in fact, sets a dangerous precedent for police behavior, because it legitimizes racial profiling.
Immigration policy is racial profiling.
They stop Latinos when they are looking for immigrants. They don't stop whites. That would mean police and the INS couldn't collaborate, and city and county resources couldn't be used to enforce immigration policy or to conduct raids. The federal immigration bill from 1996 made it easier for local police to cooperate with INS officials, even allowing INS officers to be deputized. And in the past six months, there has been an increase in INS-police raids in Washington state.