Two top Prince George's County officials, including the second in command under County Executive Jack B. Johnson (D), have been asked to testify before a state grand jury investigating the awarding of contracts, according to two government officials with direct knowledge of the inquiry.

Jacqueline Brown, the county's chief administrative officer, and Iris Boswell, the deputy chief administrative officer for the Office of Finance, are the latest, and most prominent, witnesses ordered to testify in an ongoing investigation by State Prosecutor Robert A. Rohrbaugh into the awarding of county contracts. Several former and current county employees have appeared before the grand jury in recent months.

Neither Brown nor Boswell returned calls for comment yesterday. A secretary in Brown's office said she was out of town. Boswell, according to a government source, testified yesterday.

James P. Keary, a county spokesman, said he could not confirm or deny whether Brown or Boswell has been contacted by the state prosecutor's office.

"We have been cooperating with this from the very beginning, and we will continue to cooperate with the state prosecutor," Keary said.

The investigation is the second by the state prosecutor's office into Prince George's officials in the past two years. Last year, Johnson was the subject of a six-month inquiry into whether he withheld $5 million from Prince George's Hospital Center until officials hired one of his associates as a senior manager. Johnson was cleared of any wrongdoing.

The current investigation began this year with an inquiry into an alleged scheme by senior-level managers Robert L. Isom and Robert L. Thomas to receive bribes for the awarding of a county security contract.

Isom, the former deputy director of environmental resources, pleaded guilty last month to conspiring with Thomas, the former deputy director of the Office of Central Services, and others to demand and receive a bribe.

According to court documents, Isom met an employee of Interior Systems Inc., a minority subcontractor vying for the security contract, at a restaurant and said he could introduce the employee to Thomas, who could "help ISI's team get the contract." The same day, the trio met over drinks at another restaurant and talked about Interior Systems. Isom said Thomas told him that he could control the award of the contract and that they should demand $250,000, according to court documents. ISI contacted the state prosecutor's office and cooperated with the probe.

Thomas has not been charged with a crime. Isom is scheduled to be sentenced in January and has agreed to cooperate with the state prosecutor.