Thirty-nine police recruits, nearly one-quarter of the new class at the D.C. police academy, were suspended yesterday after a urine test administered April 5 indicated they had used marijuana and, in one case, amphetamines.

The police officers, who were to graduate from the four-month training course May 7, surrendered their badges at the academy and were placed on administrative leave with pay.

They face possible dismissal, depending on the results of a follow-up urine test administered yesterday and a police internal investigation, police said.

"I am disappointed, naturally. I never expected anything like this," Police Chief Maurice T. Turner said yesterday. "But this is the culture that we are living in and we have to take precautionary measures."

Turner added, "The biggest fight we have in this city is against drugs. How can we expect a policeman who is abusing the law to enforce the law in the area giving us our biggest problem? I am glad we can weed them out of the system."

The suspensions were a major setback for the department, which is currently trying to beef up its crime-fighting presence on orders from Mayor Marion Barry and at the direction of Congress. Turner informed Barry of the suspensions yesterday, but the mayor could not be reached for comment.

Turner said the department used a highly sophisticated urine test, processed at an outside laboratory, which was sensitive enough to detect even small amounts of drug use "seven years or seven minutes ago."

Theodore R. Carr, the deputy police chief in charge of recruitment and training, said such tests have been used in other jurisdictions and have been "ruled reliable."

However, the president of the D.C. Fraternal Order of Police, Gary Hankins, said yesterday the union is concerned about the reliability of the test and about the fairness of firing a new officer for perhaps having sampled marijuana years ago.

"Nobody wants drug users as policemen. We don't either," Hankins said. "But we want to make sure the test is accurate. And we should not be concerned with 10-year-old drug use. Are we talking about a test for marijuana used last week, or that you smoked one joint 10 years ago?"

Hankins said some of the recruits were bewildered by the suspensions. "A lot of them are just in shock," he said, adding that several called the union's offices, insisting that they are not drug users and that the test must have been defective.

Hankins said he asked FOP lawyers yesterday to research the issues, including the question of the legal rights of the recruits. The police recruits are already sworn officers, but are on one-year probationary status in which they do not have the full rights of administrative appeal available to other officers.

The suspensions came after the department received results of an unannounced urine test administered to some 165 recruits on April 5. Turner said it indicated drug use by 11 female and 28 male recruits who were completing their training and awaiting their first assignments.

Urine tests have been routine for several years in the department and currently are administered at the time of recruitment and again, unannounced, during training. Another unannounced test is conducted during the probationary year.

The suspended recruits were among 178 hired last Dec. 14 under a congressional mandate to add at least 200 new officers to curb crime in Washington. About a dozen have dropped out of the class, including three who were dismissed earlier this year because they concealed criminal records. One recruit, Daphine W. Essex, 25, of Northeast Washington, was arrested at 14th and V streets NW on March 28 on charges of drug possession.

Turner said the department is in the process of recruiting a new entering class at the academy for the $17,000-a-year jobs. He said he was disappointed at the setback to his recruiting efforts, but he stressed the importance of taking a hard line against drug use within the department.