A multi-billion-dollar bidding battle for Conoco Inc. and its rich energy resources developed on a wide front today as Mobil Corp., the nation's second largest industrial company, said it might join the list of giant corporations seeking to buy Conoco, the nation's ninth largest oil concern.

The Seagram Co., a big Canadian distiller, and E. I. du Pont de Nemours & Co., the nation's largest chemical firm, already are locked in a struggle for control of Conoco. Texaco Inc., the fourth largest industrial company and third largest oil company, also is rumored to be interested in Conoco.

Banking sources said that Mobil is arranging a $5 billion loan through a syndicate led by Citibank in anticipation of making a bid for Conoco. Texaco is arranging a $5.5 billion loan, although that company may be interested in bidding for other companies besides Conoco.

"There's a feeding frenzy out there," said a major banker.

In a carefully worked statement this morning, Mobil chairman Rawleigh Warner Jr. confirmed that Mobil was arranging a bank loan. The statement said that it appeared Conoco would be sold and that "preliminary studies indicate that a Mobil/Conoco merger would not create difficulties under existing antitrust guidelines."

The Senate Judiciary Committee will hold hearings on the antitrust implications of the bidding for Conoco, Chairman Strom Thurmond (R-S.C.) said, although no date has been set. "It appears that it is appropriate to hold such a hearing," Thurmond said in a letter to Sens. Edward M. Kennedy (D-Mass.) and Howard Metzenbaum (D-Ohio), which they released yesterday.

The two senators asked for hearings, saying that the Conoco bidding "seems to be just the beginning of a long series of such huge combinations."

A Justice Department spokesman said its antitrust division and the Federal Trade Commission have not yet determined which one will review the proposed Du Pont-Conoco merger.

Wall Street analysts said that Mobil, with sales last year of $59.5 billion, likely would face a more severe antitrust scrutiny from the federal government than either Seagram or Du Pont.

Although a Du Pont-Conoco merger would create the nation's seventh-largest industrial company, with combined annual sales of $32 million, the firms overlap in only a small portion of their businesses. Similarly, there is little overlap between Seagram and Conoco.

But from oil exploration to gasoline marketing, the petroleum operations of Mobil and Conoco coincide.

Late Sunday afternoon Seagram upped the cash ante in the Conoco takeover sweepstakes. Its U.S. subsidiary, Joseph E. Seagram & Sons Inc., said it would pay $85 a share, or $3.77 billion in all, to buy 44.35 million shares of Conoco stock, 51 percent of the shares outstanding. That was an amendment of its earlier offer June 25 to pay $73 a share for 35 million Conoco shares.

The Seagram offer has been fought for nearly a month by Conoco management, and last week Conoco chairman Ralph E. Baily found in Du Pont a "white Knight" willing to engage in a friendly takeover of the oil giant.

In what would be the biggest corporate takeover in history, Du Pont said it would be the biggest corporate takeover in history, Du Pont said it would spent about $3 billion to buy 34.44 million shares of Conoco at $87.50 a share and exchange 1.6 shares of its stock for each of the remaining 52 million shares. Although in total value the proposed Du Pont offer is larger, Conoco shareholders would take home more cash from the revised Seagram bid.

If Du Pont decides to boost the number of shares it will buy for cash, it could face less pleasant consequences than it would under the proposal it put forward last week. If it acquires the majority of the company's shares for cash, tax laws will not permit Du Pont to take as big a write-off on Conoco assets as they do when the majority of the shares are acquired by an exchange of stock.

None of the principals in the Conoco spectacle would comment on today's developments. On Wall Street, however, investors were active as Conoco was most active on the New York Stock Exchange, up $7 to $84.37 1/2. Du Pont closed unchanged at $47.25, Mobil was unchanged at $31.25, and Seagram dipped 12 1/2 cents to $55.87 1/2.

Meanwhile, the amount of bank credit pledges being garnered by oil companies has grown sharply as some companies add to their ability to take over a concern and others pile up loan commitments to ward off potential suitors.