The White House announced yesterday that presidential counsel Fred F. Fielding is investigating reports that deputy chief of staff Michael K. Deaver and some associates used diplomatic passports to purchase BMW luxury automobiles at a discount while in West Germany recently on official business.

Deputy press secretary Robert Sims said White House chief of staff Donald T. Regan asked Fielding to look into the matter after Newsweek magazine reported that Deaver and a presidential advance team arranged through embassy personnel in Munich to buy nine cars, using passports to obtain discounts of about 25 percent.

A White House official who asked not to be identified said Deaver purchased one of the nine cars.

The official said that 35 persons were in the advance group planning Reagan's visit to Europe in May and that it has not been determined who purchased the other eight cars.

The official said Deaver used a diplomatic passport and received about a 15 percent discount.

The official said that no crime was committed, that the State Department considered such use of passports "commonplace."

Fielding is looking into the "propriety" of the transaction, the official said.

The official said the cars were purchased directly from BMW and noted that the manufacturer had earlier discontinued the practice of selling them in this way because of complaints from U.S. dealers.

Newsweek said Deaver explained the purchases as a traditional perquisite for those holding diplomatic passports.

Deaver has announced he is leaving the White House and told friends he intends to leave in May.

Sims said Fielding is conducting an "inquiry" into the matter and is to talk to Deaver about it "at some point."