The administration's Taft-Hartley board began preparatory work for an injunction to order striking coal miners back to work yesterday as a top White House official acknowledged that government seizure of the mines is still possible.

These developments came as:

The Bituminous Coal Operators Association, the main industry bargaining group, ran full-page advertisements in 11 newspapers accusing the United Mine Workers of holding "the nation hostage with threats of devastationg losses of power" by stopping coal production.

The United Auto Workers contributed $2 million to a relief fund for the families of UMW workers, claiming that "thousands of people spread throughout the coalfields are enduring tremendous suffering" and the UAW "cannot and will not turn its back on that suffering."

A legal controversy threatened to erupt over the administration's insistence that food stamps must be denied to ffamilies of miners who defy a back-to-work court order.

Both government and industry sources reported that coal production is increasing despite the strike, with tonnage now more that half last year's volume, reflecting a steady increase from a month ago, when it was only one-third.

Coal state governors pledged to keep the peace if the mines reopen and some warned they will use the National Guard. Virginia Gov.John N. Dalton declared a state of emergency and ordered hundreds of state police into coal areas.

An administration official said one BCDA coal company is "moving toward an independent settlement," which, if happens, could drive a wedge into the industry's united front. The official declined to identify the company, and another source said the presumed company has been in that posture for days.

The Taft-Hartley board of inquiry, appointed by President Carter Monday when he invoked the controversial 1947 law in an attempt to end the 92-day coal strike, met to prepare for a hearing today - for which more than 5,000 invitations were sent to union and industry officials.

Despite the administration's policy of openness in policy making, the board agreed yesterday to exclude the press and public from the hearing. A spokesman said the decision was made by the board without White House influence. He said reasons included limited space in the hearing room ar the Federal Mediation and Conciliation Service and possible delays that the press and public would cause.

The three-member board of labor arbitrators is expected to complete its fact-finding work and report to Carter by early tomorrow.

Within hours of that, the Justice Department is prepared to go into federal court here and elsewhere to seek injunctions barring continuation of the strike by 1 60,000 UMW members who last weekend overwhelmingly rejected a settlement reached by their leaders.

The White House has been vigorously discouraging speculation that it was holding seizure plans in reserve in case the Taft-Hartley strategy crumbled in the wake of massive defiance by the strikers, which many of them are threatening. The fear is that the miners will want to hold out for greater gains they believe they can get under temporary federaloperation of the mines.

But yesterday, in a breakfast meeting with reporters, U.S. special trade negotiator Robert S. Strauss said publicly what some lower-echelon officials had been conceding privately.

The idea of asking Congress to authorize government seizure and operation of the mines until a settlement is reached "is not out the window," said Strauss. But, he added, "we've got to have a run at this (Taft-Hartley)."

Asked when seizure might again be considered, Strauss responded: "Somewhere, you have to reach up and pull a decisiin down."

Carter had been prepared to call for both Taft-Hartley and seizure before the BCOA, at the last minute, agreed under White House pressure Feb. 24 to a contract proposal that had previously won approval of the UMW's bargaining council. But that contract was massively repudiated by rank-and-file mines last weekend, prompting a change in administration stragegy.

Another official, acknowledging that Strauss' candor caused some anguish within the administration, said seizure had never been ruled out, despite White House assurances that it was no longer planned.

"It's everyone's intention to get out of this mess without seizure," the official said. "But if it becomes clear that seizure is the only way out after a couple of weeks or so, then we'll probably go with it. There's no fixed-time, no deadline, for testing Taft-Hartley."

Taft-Hartley was used three times against the UMW between 1948 and 1950, with discouraging results: defiance in two of the three cases. The mines were federalized during World War II and for a time afterward, and President Truman broke the last Taft-Hartley coal impasse in 1950 by threatening to seize the mines.

The government's threat to cut off food stamps next month to miners who refuse to obey a back-to-work injunction raised questions on Capitol Hill and spawned reports of impending legal challenges.

"If you courts order the miners back to work and they refuse, there is provision in our regulations for terminating food stamp recipients," said Joe Sheperd, deputy director of the program. "The provision is for terminating any household that has a member in an illegal work stoppage."

Another Department of Agriculture official said the injunction would make future striking illegal. But congressional sources said courts have cast doubt on the enforceability of the departmental regulation. The law permits use of food stamps in strikes and make no distinction between legal and illegal strikes.

UMW President Arnold Miller said in an interview that he believes the government has the power to withold food stamps but added: "Our members are good taxpaying citizens and they have as much rights as anyone."

In the interview, Miller also said he thought Carter has "good justification" for invoking the Taft-Hartley Act as a speedier remedy than seizure legislation but would prefer seizure.

He blamed defeat of the contract proposal on "divisive elements" within the union which "distorted" its provisions and reiterated that he will not resign in the face of persistant intra-union demands that he step down. "I will serve out the five-year term . . . I've never run away from a fight," said Miller, adding: "We've been through this before . . . Mr. [John L.] Lewis had trouble too. He had Taft-Hartley Act invoked."