Last week, the board rejected a merger offer made by American General, which is based in Houston.

The company said the merger offer would begin immediately and be open until May 24.

In 1930, the company turned down a merger offer from rival Sears.

The oil and gas company said it had received a merger offer from an undisclosed suitor worth $12 a share.

On Thursday, Sun raised its merger offer, these people say.

The merger offer was for $15 cash and 1.675 shares, or about $65.46 a share at yesterday's stock price.

The board of Corestates has been divided over how to respond to merger offers.

There was no reaction from Unitrin, which recently rejected the insurer's merger offer.

Philadelphia, the nation's oldest stock exchange, received a previous merger offer from the Chicago board last fall.

It had previously bid $66 a share only as a friendly merger offer.