The D.C. Board of Elections and Ethics has received a confidential progress report on its "preliminary inquiry" into the financing of Mayor Walter E. Washington's 1974 election campaign, but the board wants more information before deciding if its probe should continue.

The report was presented to the board Thursday by its chief investigator, campaign finance director Carl McIntyre. Sources familiar with the report said about 10 persons had been interviewed - none of them under oath - and given investigators no evidence of improper financing in the campaign.

The Washington Post reported Dec. 23 that, according to well-placed campaign sources, $1,400 in secret cash payments was used to pay salaries of campaign workers and not reported as required by law.

The Post reported Jan. 5 that the mayor and top officials of the campaign agreed last year to pay $5,400 in campaign-related equipment rental, supplies and legal expenses that were also not reported.

On Dec. 27, the board voted to conduct a "preliminary inquiry" into the allegations in The Post to determine if a full-fledged investigation ws warranted. McIntyre's preliminary report recommended that no further investigating be done, sources said, but the board considered such a decision on the information in the report insufficient for making such a decision.