Senior officers from Humberside Police have become the first in the force to undergo random drug testing.
A new substance misuse policy has been introduced across the force.
After completing the tests, Chief Constable Tim Hollis said: "Quite understandably people expect the police to meet high standards of behaviour.
"As Chief Constable I am committed to achieving those standards and to ensuring a safe, healthy and productive work environment for all my staff."
He continued: "The random substance misuse testing will apply to police officers undertaking critical roles where there would be a significant risk if they were subject to substance misuse."
Under the policy, officers and staff can be tested if they work in an environment which is deemed safety-critical or specialist.
Among those subject to random testing are officers and civilian staff who are firearms trained, work in the drugs squad, divers, drivers, motorcyclists and dog handlers.