By Bill Dedman, msnbc.com, and Michael Isikoff, NBC News
with reporting by NBC's Azriel Relph and Lisa Riordan Seville

Hollywood director Steven Spielberg and the Service Employees International Union were among the big donors to a Super PAC supporting President Barack Obama. Priorities USA Action filed the report Tuesday with the FEC showing $4.4 million raised to support the president's re-election.

Spielberg chipped in $100,000, and the SEIU gave the largest amount,  $1 million.

The total contributions to Priorities USA Action are, however,  far less than those being raised by the Super PACs for the Republican candidates and appear to put the group well behind its initial goal of raising $100 million on behalf of the president's re-election.

But there are signs that the Obama Super PAC is being financed by a related non-profit group that is in turn raising money from secret donors. Such non-disclosing political entities were denounced in 2010 by President Obama. But in Tuesday night's filing, the pro-Obama Priorities USA Action reported that it has gotten $215,234 from its non-disclosing sister group, Priorities USA, listing the funds as reimbursements for its operating expenses. As a nonprofit, Priorities USA is not required to file any public reports with the Federal Election Commission.

Proirities USA Action and Priorities USA, which has already begun running attack ads on Mitt Romney,  were founded last year by two former Obama White House aides -- former deputy press secretary Bill Burton and political aide Sean Sweeney. Burton said in an email to NBC News that the two groups Priorities groups together have now raised a total of $6.7 million, adding: "I have no doubt we'll raise our goal. The question is when we'll raise it."

The SEIU, which organizes workers in government jobs, health care and property services, has been a strong supporter of Obama. Its leaders have been named among the most frequent visitors to the White House, when the Obama administration released most of its visitor logs.

Other donors to the Obama Super PAC include:

 The American Association for Justice PAC has contributed a total of $50,000 to the PAC, and has also given a total of $100,000.00 to the House Majority PAC, which supports Democrats.

John C. Law is the managing director of Warland Investments, a major landowner in Cypress, Calif. He has given $100,000 to Priorities USA, and is a big donor to Democratic political causes.

Akerman Senterfit is a law and lobbying firm with locations throughout the U.S. Records show $20,000 going to Priorities USA from the firm, and another $10,000 from Joseph L. Falk, who specializes in the mortgage banking industry at the firm.

William E. Little Jr. gave $150,000. He is chairman of George Little Management, LLC, a large producer of trade shows for consumer goods in the United States, and a Bates College trustee.

Lenny Mendonca gave $50,000. He is a direcdtor in the San Francisco office of McKinsey & Co., chairman emeritus of the Bay Area Council, and chairman of the Bay Area Council Economic Institute. He is the former chair of Repair California, the organization behind the call for a limited Constitutional Convention to address the structural elements that have made governing California so difficult. He serves on the board of The New America Foundation.

The full list is here.

Tuesday is the day for the so-called Super PACS to file an annual report of donors. NBC News and msnbc.com will be scouring the filings, and posting details. We'll have updates on msnbc.com, and could always use your help identifying the economic and political interests behind the names.

The official deadline for filing is midnight ET (12 a.m. Wednesday), so reports may trickle in. And it wouldn't surprise us if some campaigns file late tonight as attention is focused on voting results in the Florida Republican primary.

Super PACS are known to the Federal Election Commission as independent committees, because they are forbidden to coordinate their activities with campaigns. Outside the limits of campaign finance laws, Super PACs may raise unlimited sums of money from corporations, unions, associations and individuals. They can use that money to advocate for or against political candidates.

Read more about the reports filed Tuesday:

After TV cameras leave, Romney PAC discloses $18 million

Perry PAC's $1 million donor got help with nuclear waste dump

Major GOP Super PAC raised $51 million in 2011

Not 'Desperate' for cash: Obama lists his big fundraisers

Sugar Daddy: Huntsman's father gave $1.9 million to Super PAC

Colbert Super PAC raises $1 million; non-satirical PACs to follow