WASHINGTON — The Federal Trade Commission is in the advanced stages of its investigation into whether Facebook violated privacy rules and is expected to seek large fines from the company, according to two people familiar with the inquiry.

The five members of the commission met in mid-December to discuss the investigation, according to the people, who would speak only on the condition of anonymity because the investigation is not public. The meeting is a sign that the investigation is far along, the people said, because the commissioners rarely meet in the early stages of an inquiry.

The investigation, which began in late March, is continuing, and the commissioners and staff have not reached a final conclusion, including how much the agency might seek in fines, the people said. Consumer-protection and enforcement staff members have provided updates on what they believe is evidence of privacy violations, but they have not submitted a final report.

The commissioners would vote on any recommendations from the staff, including whether to pursue fines or other penalties. They do not always approve staff recommendations.