An ethics committee extended its inquiry Thursday into one of the Senate's most powerful members, making the decision behind closed doors with no timetable to end the investigation.

The Senate Ethics Committee announced last month that it had "substantial cause" to believe state Sen. Don Balfour violated the chamber's rules regarding travel and per diem payments.

At the time, it indicated that negotiations would begin with the Republican from Snellville on a possible settlement.

But in a statement released after the private two-hour meeting Thursday, committee Chairman John Crosby, R-Tifton, said that instead the committee "initiated further investigation and following today's meeting will be serving Senator Balfour with an amended complaint."

Crosby declined in person to answer questions about the investigation. It was not clear in his statement whether the committee had expanded the complaint to include other violations. Among issues not previously addressed by the committee is the fact that Balfour, as longtime chairman of the Senate Rules Committee, did not heed state law requiring an audits subcommittee.

The Rules Committee must have an audits subcommittee, the law says, "to examine and review, not less than once every two months, legislative expenditures, including all vouchers submitted by members of the Senate, as provided for in this Code section, for which the members have received payment."

Balfour is accused of billing the state for mileage while out of town on lobbyist-funded trips. He did not attend Thursday's meeting and did not return messages seeking comment. He has amended a number of reimbursement claims this year after acknowledging mistakes.

Among the penalties Balfour could face is censure by the committee. A hearing — something akin to a trial with Balfour allowed to present a defense — also could be set.

Penalties in state law for willfully falsifying legislative expense reports include a fine up to $1,000 and as much as five years in jail. State authorities, however, have not said whether they have any interest in pursuing the case. The attorney general's office declined to comment Thursday.

Balfour faces two GOP challengers in the July 31 primary. With no deadline to end the investigation before then, William Perry, executive director of Common Cause Georgia, said the committee's secrecy about the investigation is hurting voters.

"This is a Legislature that talks a lot about their transparency, and this is certainly not a transparent process," Perry said. "It's important to come to a rapid conclusion about this stuff — out of fairness for Senator Balfour, but also out of fairness for the voters who are trying to make a decision of electing a senator who they believe is ethical."