NEW YORK, JULY 2 -- The Securities and Exchange Commission has stepped up its probe of possible securities law violations in connection with an attempted takeover last year of TRE Corp.

The SEC issued a formal order of investigation on June 16 and has sent out related subpoenas, sources familiar with the case said today.

Investigators are looking at a 1986 bid for control of TRE, a California aerospace company, by Hollywood producer Burt Sugarman. TRE was acquired for $330 million in December 1986 by Aluminum Co. of America, after Sugarman's bid through his Giant Group Ltd. put TRE under pressure.

The probe is focusing on whether Sugarman and his financial advisers, including Drexel Burnham Lambert Inc. and the Jefferies & Co. stock brokerage firm, failed to disclose that they were working together or with others as part of an investor group seeking control of TRE, sources said. One major investor in TRE stock during this period whose activities are also said to be under review was New York investor Saul Steinberg, who made about $4 million when he sold his shares to Alcoa.

Drexel has received a subpoena in connection with the probe, sources said.

Sources said the investigation also is focusing on whether Sugarman filed financing documents that failed to disclose his intentions toward TRE. Sugarman raised about $35 million in the spring of 1986 with the help of Drexel and Jefferies. Some of the money was used to buy TRE stock. But Sugarman made no mention of TRE in the financing documents.

The SEC probe also is examining whether TRE stock was purchased on the basis of confidential, inside information and whether investment advisers may have helped Sugarman conceal the true ownership of TRE shares through a "parking" scheme.

Boyd L. Jefferies, the former head of the brokerage firm bearing his name, recently pleaded guilty to charges that he helped stock speculator Ivan F. Boesky conceal ownership of shares in takeover targets. Through the scheme, Boesky sold shares to Jefferies but secretly agreed to buy them back at a later date, in violation of federal law.

One source said today it was possible that Boyd Jefferies' cooperation with the government probe has provided fresh information about dealings in TRE stock. This could be one of the reasons the SEC elevated the probe to formal status and issued subpoenas.

However, the SEC may have stepped up the investigation because of discoveries from other sources or to question witnesses under oath as part of a formal proceeding. The informal probe was disclosed in February.

At the time, a spokesman for Drexel said, "We were not involved in Sugarman's investment in TRE." Other sources familiar with the transaction said that after Sugarman disclosed his initial stake in TRE in May 1986, he asked Drexel to help him raise funds that could be used to buy more TRE stock, but Drexel, which had helped him raise $35 million, turned him down.

The formal order of investigation in the matter of "Trading in the securities of TRE Corp." does not specify who is the target of the SEC probe. However, it specifically raises questions about trading and disclosure by Sugarman's Giant Group.

The order names Drexel and Jefferies in connection with financial disclosures under review. It does not mention Steinberg. A spokesman for Steinberg has said he made his purchases of TRE stock solely on the basis of a recommendation from one of his stock analysts.