Chemistry Board

Fiat SpA said it would raise its stake in Chrysler Group LLC to 61.8% from 58.5%, cementing its control of the U.S. auto maker on which it is increasingly reliant as Fiat sales in Europe wilt.

Chrysler, which undertook deep production cuts before its bankruptcy in 2009, has been steadily adding back workers and expanding production at its North American plants under the leadership of Chief Executive Sergio Marchionne who is also head of Fiat. In the U.S.