Almost 300 high-ranking federal police officers in Mexico have been temporarily suspended in a bid to tackle corruption within the force.
Dozens of federal officers have worked for Mexico's drug cartels
Officers will face a "trust test" which will include drug checks, a lie detector and psychological tests.
Mexico's president has made the fight against drug traffickers one of his key priorities since coming to office.
The move is one of the most radical measures yet undertaken by authorities to stamp out corruption.
Mexico's public safety secretary said that the friends and families of officers may also be investigated and officer's bank records checked.
"There are mafias that don't want the situation to change so they can continue to enrich themselves under the protection of corruption and crime," said Public Safety Secretary Genaro Garcia Luna.
Dozens of federal officers have been found to be working for the country's drug cartels over recent years.
Those who fail the tests will lose their jobs but those who get the highest marks will be promoted to regional federal police chiefs.