Thirty-eight people were arrested in Washington and Baltimore this week in two separate investigations of food stamp trafficking, in which vouchers were illegally exchanged for crack cocaine, heroin and cash, federal agents said.

A six-month investigation in the District uncovered deals in which $93,000 worth of food stamps were illegally exchanged for about $17,000 in cash and an unidentified quantity of cocaine, federal investigators said.

The investigation in Baltimore linked store owners, employees and associates of retail stores authorized to deal with food stamps to illegal profiteering. Four people were charged with accepting food stamps from undercover federal agents in exchange for heroin and cocaine.

The investigations are part of a nationwide effort by the U.S. Department of Agriculture to break the growing link between the illicit drug trade and the food stamp program, which is designed to supplement low-income households.

In the District, three employees of public libraries were arrested yesterday after they traded $1,605 in cash for $3,865 in food stamps with undercover USDA agents, according to the USDA inspector general's office.

Patricia Gorham, 27, of the 800 block of Carson Avenue, Oxon Hill, and Carrie Sampson, 37, of the first block of Bates Street NW were arrested at 3:45 p.m. while working at the Southeast library branch after allegedly paying cash for stamps offered by an undercover agent. The transaction occurred in the library's first-floor meeting room, according to a USDA spokesman.

"Our agent gave them the food stamps. And they gave him the cash," said Kim Widup, supervisor of special agents. The two women left the library, at Seventh and D streets SE, with the agent and were arrested.

About 40 minutes later, agents arrested Gorham's husband, Bobby Ray Gorham, 39, while he was working at the Martin Luther King Jr. Library at Ninth and G streets NW. All three were charged with unauthorized possession and acquisition of food stamps.

Three other people were arrested the previous evening at the corner of Sixth and G streets SE after exchanging 7 1/2 ounces of crack for $40,000 in food stamps from USDA undercover officers, according to the agency.

Investigators identified those arrested as: Joseph Day Henson, 62, of the 500 block of G Street SW, Apt. 11; Vivian Sue Davis, 51; and her husband, Charles Davis, 69, both of the 2700 block of Angier Place SE.

Widup said the arrests occurred about 6 p.m. after Henson arranged a deal with two agents and the Davis couple.

In Baltimore, 32 people were charged with food stamp trafficking, theft and distribution after a nine-month investigation. Thirteen of them were indicted by a federal grand jury on various counts of unauthorized possession and redemption of food stamp coupons, distribution of narcotics and conspiracy.

The remaining 19 were charged in District Court in Baltimore on similar counts. Store owners accepted food stamps for approximately half value -- in cash or drugs -- and redeemed the food stamps through the government for face value, officials said.

Under federal law, the maximum penalty for unauthorized possession or acquisition of food stamps is five years in prison and a fine not to exceed $250,000.