While only two parties have expressed an interest in buying the Mercury News and other Northern California Knight Ridder newspapers, a bidding war has erupted for the chain’s papers in Philadelphia, according to a report by Joseph N. DiStefano of the KR-owned Philadelphia Inquirer. The latest group that is kicking the tires of the Philadelphia Inquirer and Daily News is from Canada, and includes the chairman of the CanWest newspaper chain. CanWest owns two national dalies, several dailies in major cities and a national TV network. Another potential bidder is a group headed by developers Brian Tierney and Bruce Toll of the Toll Bros. home construction company. Billionaire Ron Burkle, who is financing a union-buyout proposal, is also bidding for the Philadelphia papers, as he is for all of the Knight Ridder papers up for sale. Dean Singleton, who is thought to have the inside track to buy Knight Ridder’s papers in Northern California, balked at the price for the Philadelphia papers last month, and so now they’re being offered to the other bidders. [E&P: Interest in Phily papers grows as visitation week begins]