ZURICH - Switzerland’s top technology institute says a U.S. chemist has resigned as head of research after scientific data were found to have been manipulated.

The Swiss Federal Institute of Technology, or ETH, says Peter Chen acknowledged responsibility as head of the research group that published the doctored data in 1999 and 2000.

ETH says it has not established who manipulated the data. It said Monday that Chen would remain at the Zurich-based institute.

Chen studied at the University of Chicago and completed his doctorate at Yale before moving to Harvard in 1988. He joined ETH - one of the world’s top research institutes - in 1994.