The District of Columbia official in charge of liquor licenses and building inspections and his top aide were placed on administrative leave yesterday after federal prosecutors informed Mayor Marion Barry that the two men are targets of a grand jury investigation that sources said involves allegations of bribery and extortion.

Robert C. Lewis, who holds cabinet rank as director of the Department of Licenses, Investigations and Inspections and chairman of the Alcoholic Beverage Control Board, and James E. Boardly, staff director of the board, were placed on leave pending the outcome of the investigation, city administrator Elijah B. Rogers said.

Sources with the month-old probe said it centers on allegations that the two attempted to secure a personal interest in operations at the new Hechinger Mall at H Street and Bladensburg Road NE in exchange for favorable consideration in liquor and buildings licensing.

Rogers, in anouncing that he had placed the two men on leave, said only that the probe involved "alleged improper conduct . . . during the course of their official duties."

The sources said that the investigators are looking into allegations that one or both of the officials approached represenatives of businessman John W. Hechinger, developer of the mall, and told them that it would be difficult to get the necessary licenses unless the officials were given an interest in the project.

"It involves talk that life could be made more difficult in terms of licensing unless the Hechinger people did business with them." said one source familiar with the allegations under investigation. "It involves assurances that licenses could be delivered under the right circumstances."

The grand jury is also expected to hear allegations that Lewis and Boardely wanted Hechinger's to grant a liquor franchise in the mall to a person selected by the two officials, and investigators are trying to determine who might have shared in the profits of such a franchise, sources said.

Sources reported that the unnamed represenatives of Hechinger Enterprises and their lawyers, including Eugene M. Propper, contacted U.S. Attorney Charles E.C. Ruff to report what they thought might be a possible violation of law, thus triggering the investigation.

Hechinger declined to comment on the investigation last night, saying only: I know a little bit about this, but that's all I can tell you."

The Hechinger Mall complex, financed in part by a $3.2 million federal urban development grant, is considered by city officials as the centerpiece of their plan to revitalize the riot-torn H Street NE corridor and a large swathe of Northeast Washington .

The $13.3 million project, which partially opened Feb. 1, has been the subject of protest by some neighborhood organizations who feel that minorities and neighborhood groups are underrepresented in the construction crew building the project and the ownership of stores in it.

When completed, the mall will contain liquor stores and restaurants, both of which would need liquor licenses issued by the ABC board in order to operate.

Ruff called Barry yesterday morning, Rogers said, and told him of the investigation. Federal investigators used grand jury subpoenas to obtain several boxes of city license records, which were later presented to a grand jury.

Barry, Rogers, Corporation Counsel Judith W. Rogers and Herbert O. Reid, the mayor's legal counsel, met for more than an hour late yesterday before emerging with the announcement that the two officials had been put on leave.

Elijah Rogers said the administrative leave was involuntary, and said the two men stated that they believed they would eventually be vindicated. Such leave can last no longer than 10 days. After that time, the men must take annual leave in order to avoid an adverse personnel action that would be a permanent part of their record. Neither Lewis nor Boardley could be reached for comment yesterday.

"These are two very sensitive position," said Elijah Rogers, in explaining why the city's action in placing the two men on leave came so swiftly,

Lewis is a 41-year-old-pipe-smoking architect and urban planner who formerly worked for the city as coordinator for the Fort Lincoln New Town project in Northeast. After Barry was elected Mayor, he worked on the mayor's transition team.

He was appointed by Barry to head the license office in January 1979, as part of a major shakeup of several city government offices, replacing Julian R. Dugas, a poitically powerful and longtime ally of former Mayor Walter E. Washington.

Within a month, Lewis had reorganized the license office staff, demoting deputy director James W. Hill, who was a close associate of Dugas. On the ABC staff, Lewis demoted the top two staff members and named Boardley, then a staff investigator, to head the office. Lewis said at the time that the changes were "a device to improve morale and efficiency."

The licensing and investigations department has wide jurisdiction that includes control over most construction, building and business permits. In addition, the three-member ABC Board controls the issuance and regulation of all liquor licenses.

Elijah Rogers announced that Carol Thompson, formerly Lewis' special assistant, has been named interim director of the department.

The investigation is being coordinated by the fraud and major crimes office here and involves agents from theWashington field office of the FBI. o