The Lacaz-Gardner School of Business was formally ordered to close by the D.C. fire marshal Monday, following two major fires at the school last Thursday and a series of smalled trash fires there earlier last week, a spokesman for the fire marshal said yesterday.

Lt. Jack Fletcher said that a letter containing the order was hand-delivered to Daniel Grossman, owner of the school at 710 14th St. NW, Monday morning ordering him to cease operations of the school until all fire hazards in the building have been corrected.

Fletcher said the school was already "making some corrections" on a wide-range of deficiences found in the school in June. He said the corrections would involve extensive construction work to further fireproof the building.

"We felt that the controversy surround the school, there was a great chance that more fires might break out in the school," said Fletcher.

Two fires erupted in Lacaze-Gardner buildings at 710 14th St. NW and at 1424 New York Ave. NW Thursday morning, after an announcement by the school on Wednesday that no additional students would be accepted at downtown classrooms and that the downtown school would close in July.

Fletcher said that fire officials investigating the major Lacaze-Gardner fires on Thursday were told there were three trash can fires in the school that Monday and at least one other fire in a trash can on Tuesday. The trash fires were not reported, he said.

The Lacaze-Gardner School has had several problems in recent months. In May, the U.S. Office of Education found in a routine review of the school's files that Lacaze-Gardner was receiving unusually large amounts of money through federal student financial aid programs, that the dropout rate was 80 percent and that some financial aid records were not accurate, among other things.

The Office of Education announced in September that it was investigating the school for possible abuse of federal student financial aid programs. The FBI has since launched an investigation into the school's affairs.

Last Wednesday, Grossman abruptly announced without explanation that the school would close by July 1979. On Monday, the school's entire faculty of 21 teachers said they had been fired over the weekend by Grossman, who lives at the Watergate Hotel and drives a Rolls-Royce. Also on Monday, about 100 students arrived for morning classes to find a handwritten notice that the school was closed "until further notice."

The abrupt closing of the school has left the 900 students enrolled there uncertain that they will be able to continue their education.

A group of 25 students, most of whom said they were scheduled to graduate from Lacaze-Gardner later this year, went to Mayor Walter E. Washington's office yesterday to seek help.

Warren Graves, an assistant to the mayor, told the students he would consult with various city agencies to determine what could be done to help some of the students possibly to continue their education in public technical high schools and at other institutions.

Graves also advised the group to file complaints against Lacaze-Gardner with the D.C. Office of Consumer Protection.

Winston Yallery-Arthur, an attorney and spokesman for the consumer protection agency, said that as a result of recent fund cuts, the office lost half of its 40-member staff. He said the additional Lacaze-Gardner cases would be a burden, but that special arrangements were being made to handle them.

George Montgomery, 27, who enrolled at Lacaze-Gardner in August, said he has maintained a high B average in his study of business management and accounting. By June, Montgomery said he would have received his Lacaze-Gardner diploma and hope to take a job managing a retail store.

But now, Montgomery said that his future is in doubt. As he trailed around the city office building with other students yesterday in search of a remedy for his problem, he expressed bitterness.