Austrian-Canadian auto parts maker Magna International Inc. (MGA) has presented a "first interesting, rough plan" for General Motors Corp.'s (GM) European unit Adam Opel GmbH, German Economics Minister Karl-Theodor zu Guttenberg said Tuesday.

Speaking after a meeting with officials from Magna, such as Co-Chief Executive Siegfried Wolf, zu Guttenberg said the plan now requires reliable figures. Media reports have said Magna is working on a bid to take a stake in Opel.

Press reports have also said Fiat SpA (F.MI) is close to a deal with Opel and it reportedly plans to keep all four Opel plants in Ruesselsheim, Bochum, Kaiserslautern and Eisenach. The Italian carmaker's Chief Executive Sergio Marchionne has said he is open to giving Opel "a hard look" but said Fiat has "nothing to announce" regarding those reports.

Zu Guttenberg said he has conducted similar talks with Fiat, but the Italian carmaker's plan lacks sufficient figures.

He called on GM to "finally present hard numbers."

"Providing these figures and facts can't be done from our side but must most of all be done by General Motors," he said.

Talks between GM and interested investors in GM Europe and Opel will be conducted in the coming days.

"As a result, there must be an industrial plan that will be presented to us," he said.

Zu Guttenberg said the government is talking with "all potential investors" and could provide state guarantees, but this depends on an industrial plan for the company.

A person close to the talks said Magna is interested in acquiring up to 25% in GM Europe.

-By Andrea Thomas, Dow Jones Newswires; 49-30-288-8410; andrea.thomas@dowjones.com