Chancellor Helmut Kohl's government said Saturday it was investigating whether Lothar de Maiziere - East Germany's last leader and now a member of Kohl's Cabinet - worked for the dreaded secret police, or Stasi. De Maiziere denied the allegation.

Government spokesman Dieter Vogel said the decision to investigate was made after a "reference to a document was found on a file card, under the cover name `Czerny,' with an address listing" in former East Berlin that is identical to de Maiziere's. The index card was discovered among documents of the Stasi, said Vogel.Earlier Saturday, the news magazine Der Spiegel said it had uncovered records indicating de Maiziere had been an "unofficial worker" for the East German secret police using the cover name "Czerny."

Vogel did not comment on the card's authenticity or give further details about it.

Vogel said that "in agreement with de Maiziere" the Stasi files would be examined to try to clear up the matter. De Maiziere issued a statement denying he had worked for the Stasi.