Fireman’s Fund increased its stake in A & A.

The insurer, whose headquarters is in the Northern California town of Novato, revealed that it holds a 10.9% stake in Alexander & Alexander Services Inc.--news that boosted the NYSE-listed stock of the nation’s No. 2 insurance broker to $25.75, up $3.25, on takeover speculation. Fireman’s Fund said that it planned to seek Securities and Exchange Commission approval to increase its holding to 15% but professed no interest in seeking control of the firm, which a spokesman called “a terrific investment.”