The University of Michigan's Feb. 13 consumer sentiment index -- a widely followed economic barometer whose release often creates big swings in the stock market -- reached unspecified recipients prematurely, the school said Tuesday. Diane Swanbrow, a spokeswoman for Michigan's Institute for Social Research, which compiles the consumer sentiment report, says the investigation is being conducted in conjunction with law enforcement agencies. The university said it was unable to comment "beyond noting that a full review of all security measures has been initiated. New security measures have been implemented, and the last two releases have remained secure." The probe is focusing on the early release of information from the school's Feb. 13 consumer sentiment report, which showed an unexpected drop in consumer confidence. The S&P 500 closed at 1146 on Feb. 13, down from 1152 the day before. "What happened is very troubling to us, and we want to assure the public and research sponsors that we regard the security and confidentiality of U-M research data as matters of the utmost seriousness," Fawwaz Ulaby, Michigan's vice president for research, said in a statement released by the university.