(Adds cancellation of treasury shares.)
FRANKFURT, March 17 (Reuters) - Activist investor Cevian's stake in German industrial services group Bilfinger grew to 29.5 percent from 25.6 percent, a regulatory filing by Bilfinger showed on Friday.
That brings it close to the 30 percent threshold at which investors are forced under German law to make a full takeover offer.
In a separate statement, Cevian said its holding in Bilfinger rose because of the cancellation of treasury shares, adding that neither its own funds nor debt funds have been used to exceed the 25 percent threshold.
Cevian, which has a policy of buying stakes in companies whose parts it sees as being more valuable than the whole, started buying Bilfinger shares in 2011.
It instigated a management overhaul in 2015 after the group issued six profit warnings in a year, having run into difficulties in a shift from construction into services. (Reporting by Maria Sheahan; Additional reporting by Andreas Cremer; Editing by Christoph Steitz and David Goodman)