General Motors Co. said Monday it will invest $336 million in a Michigan plant that will build its new rechargeable electric car called the Volt due in showrooms next year.

GM officials outlined the automaker's investment in an existing factory that straddles the border between Detroit and the tiny enclave of Hamtramck.

The state of Michigan last year approved $135.2 million in tax incentives for a new Flint engine plant that will build engines for the Volt and to upgrade four other facilities including the Detroit-Hamtramck plant.

Counting Monday's announcement, GM's combined Volt-related investment in Michigan totals $700 million at eight facilities.

GM Vice Chairman Bob Lutz was expected to make the announcement, but didn't attend the event. Two GM spokesmen said Lutz had a scheduling conflict.