A Montgomery County police officer engaged to marry a convicted drug dealer was charged with helping him operate a cocaine trafficking ring.

Delores Culmer, 37, a patrol officer, used law enforcement databases to access information for her fiance, according to federal officials. In once instance, she ran license plate numbers associated with a man who owed her fiance drug money, authorities said. She also allegedly helped him conceal the cash he earned dealing.

Culmer, of Silver Spring, was hired by Montgomery County police in July 2003, officials said. She has worked as a community services officer, has helped with presentations on women’s safety and participated in programs for at-risk teenagers, according to a biography on a county Web site that police said she wrote.

Her fiance once told a confidential informant that Culmer kept him informed about “law enforcement moves against him,” according to a criminal complaint filed in U.S. District Court in Greenbelt. Another time, he bragged that he could find anyone at any time.

Culmer was arrested Wednesday morning after a ruse designed to catch her off guard, officials said. She was told to go to her department’s Family Crime unit in Rockville to assist in an investigation, they said.

Culmer was suspended from the department, and county officials were in the process of halting her pay. Federal officials said she has been detained pending a hearing scheduled for Friday.

“It’s shocking, and it’s hurtful,” Capt. Paul Starks, Montgomery County police spokesman, said of the allegations. “We have a department of about 1,600 people. Of course all of them are affected, and so is the community.”

Andrew R. Szekely, Culmer’s attorney, declined to comment.

Federal authorities did not identify Culmer’s fiance. Prosecutors said in court papers that he has two drug convictions in Pennsylvania and has spent time behind bars. One informant told police that the man transported large amounts of drugs among Arizona, Ohio, Pennsylvania and Maryland.

The two met in Pennsylvania, where Culmer previously worked as a police officer in Pittsburgh, according to the criminal complaint.

The fiance gave Culmer expensive gifts, including an engagement ring worth about $100,000, court papers say. He also allegedly gave her $30,000 in drug proceeds that she used toward the down payment on a Silver Spring house.

Montgomery police’s internal affairs unit received a tip about Culmer last year, said Police Chief J. Thomas Manger. That led to a criminal investigation. “It became clear to us that this was going to be a fairly wide-ranging investigation,” said Manger, whose department soon notified federal prosecutors.

In court papers, federal prosecutors describe records checks they allege Culmer made to help her fiance’s drug trafficking organization. In November 2009, for instance, they said she looked up two vehicles that belonged to the girlfriend of a customer who owed her fiance money for drugs. The checks revealed the girlfriend’s address in Pennsylvania.

Culmer faces charges of conspiracy to distribute cocaine and fraud in connection with computer use. “You never think that one of your police officers is going to get involved in activity like this,” Manger said.

Staff researcher Magda Jean-Louis contributed to this report.