The Justice Department yesterday launched an investigation into a threatened cross-country gas station shutdown for possible antitrust violations.

John H. Shenefield, assistant attorney general in charge of antitrust enforcement, said the government would seek civil injunctions to halt next week's proposed shutdown if it finds any antitrust violations.

Shenefield also warned that if civil court actions are taken and still fail to halt the shutdown, the government could take criminal action against gas station owners and organizers of the protest.

But it is more likely, he said, that if a determination of antitrust violations is made, the gas station owners who close could be subject to treble damage suits from consumers.

Industry sources say the shutdown is planned for May 17-20, and will likely occur in several parts of the country. California is the most-mentioned target for the action. The sources said they knew of no plans for a shutdown in the Washington metropolitan area.

The Justice Department announcement comes at a particularly bad time for gas stations owners, who have been put in the middle during the latest gas crunch.

The House of Representatives Thursday rejected giving the White House standby authority to impose gas rationing. And in several areas of the country, long lines are forming at gas stations which have been cutting back on hours and days for service.

The allegation of a possible conspiracy in restraint of trade was greeted with criticism from the gas retailing industry, although all major national industry associations have refused to endorse the shutdown.

"That's great," Jack Blum of the Independent Gasoline Marketers' Council said in sarcastic tones when told of the Justice Department announcement. "We're always glad to see the antitrust division alert and on the ball, ready to tackle problems in the energy industry that are at the heart of the issue.

"Where were they on questions like divestiture, pipelines and the Department of Energy pricing regulations that virtually destroyed independent competition? Where were they when the problen began?"

Blum said the gas retailer is "the guy caught in the middle. The entire system is coming to the point where the retail dealer is the guy who decides who gets gas and who won't.

"Everybody else, including the state and federal governments, have abdicated their responsibility of having serious conservation proposals and left us with this wild west scene at gas stations. I don't blame the dealers for fighting back."

Still, Blum said, his organization has not been involved in "any mass station closings or even encouraged them."

Risque Harper, executive director of the National Congress of Petroleum Retailers, said a group of about 35 retailers representing some 10 states met last Monday in St. Louis to listen to the problems of California retailers. "We've tried to stop that meeting," Harper said, "but they have a genuine problem. Retailers are being squeezed between 1974 profit levels and being placed on allocation by suppliers."