Two firms raised their bid for Anderson, Clayton.

Bear, Stearns & Co. and Gruss & Co., which are seeking to buy the food products conglomerate, said they increased their offer for the Houston-based concern to $56 a share in cash from $54, for a total of $683.2 million. The move by the two New York investment firms intensified a tangled struggle with Anderson, Clayton & Co., which has been been attempting to thwart the takeover.