Two key figures in a federal investigation of Maryland state construction contracts worth millions of dollars were charged with felony offenses in court papers filed yesterday, the most dramatic development to date in a long-running probe involving a former influential state senator.

The FBI's interest in Thomas L. Bromwell has for two years been the subject of wide speculation in Annapolis, where the Baltimore County Democrat was a powerful figure in the state legislature before he resigned in 2002 to lead a state agency. The charges filed yesterday are the most public indication yet that the investigation has gained momentum.

Charges of mail fraud and filing a false tax return were lodged against Michael C. Forti, a former partner with Poole and Kent, a prominent building company that won lucrative state contracts when Bromwell was chairman of the Senate Finance Committee. A charge of filing a false tax return was filed against his wife, Geraldine E. Forti, owner of a contracting firm that once employed the senator's wife, Mary Pat Bromwell.

The charges allege that the couple knowingly filed a tax return inaccurately reporting their income for the year 2000 as $1,093,780. The mail fraud count accuses Michael Forti of defrauding "various governmental and private entities," using an account held in the name of Namco Services Corp., the firm that Geraldine Forti incorporated and that, according to financial disclosure reports, employed Mary Pat Bromwell in 2001 and 2002.

Clerks in U.S. District Court in Baltimore said that neither defendant appeared yesterday and that no future court appearances had been scheduled. The two were charged under what is known as an information, a charging document ordinarily used when a defendant has agreed to plead guilty.

Attempts to reach Michael and Geraldine Forti at home yesterday were unsuccessful.

An attorney for Bromwell, Robert B. Schulman, declined to comment yesterday, saying he has not seen the charging documents.

At least a handful of Bromwell's former staff members and Senate colleagues have appeared before the grand jury examining the senator's ties with Poole and Kent. Questions have focused on state contracts given to the contractor during the years when Bromwell was in the Senate, including work the company did on a University of Maryland Medical Center building and on the construction of a $41 million juvenile justice center in Baltimore -- a contract for which the company was not the lowest bidder.

One former member of the medical center board told The Post that questions from the grand jury focused on which projects were put out for bid, how those bids were handled and who had final say over contracting decisions. The source asked not to be identified because of the sensitive nature of grand jury proceedings.

The medical center's Harry and Jeanette Weinberg Building, which opened in 2003, was paid for with private donations and more than $90 million in state funds.

Nelson J. Sabatini, who served as executive vice president of the University of Maryland Medical System during construction of the building, yesterday described Bromwell as one of his "very best friends" and said he believes the former senator is being "railroaded."

"Tommy has never, ever asked me to do anything that is wrong," Sabatini said.

Poole and Kent, which claims revenue averaging more than $180 million a year, said yesterday that it had no comment. According to regulatory filings, the firm is a target of a grand jury investigation centering on its use of minority- and women-owned businesses.

As first reported in the Baltimore Sun, Poole and Kent, which specializes in large commercial projects, installed the plumbing and ventilation systems in Bromwell's home in 2000. Bromwell belatedly listed a debt to the firm in a 2002 financial disclosure statement.

Bromwell, a one-time tavern owner, rose through the ranks to become chairman of the Senate Finance Committee. He left the senate to head the state's Injured Workers Insurance Fund, where he received a pay package worth more than $250,000 a year.

Thomas L. Bromwell, left, in 1996 with Maryland Senate colleagues Michael Collins and George W. Della Jr., now heads a state agency.