Two of the three casinos operating in Maryland, including the state’s largest, have failed for years to file disclosure forms detailing their campaign contributions and lobbyists, most recently missing a deadline before a special session on gambling.

Maryland elections officials said they did not receive required filings by the Aug. 6 deadline from the owners of Maryland Live! in Anne Arundel County or the Casino at Ocean Downs near Ocean City. The operators of both facilities had millions of dollars at stake in a special session that started a few days later.

On Wednesday, after multiple inquiries from The Washington Post, an affiliate of the Cordish Cos., which owns Maryland Live!, filed a late form listing $5,500 in campaign contributions. Elections officials said the filing could result in a fine because it was late. Company officials did not respond to requests to explain why the form, which included contributions since 2010, was tardy.

William Rickman, the owner of Ocean Downs, did not respond to several inquiries this week from The Post, both directly and through his Annapolis lobbyist.

A representative of the public-interest group Common Cause called the lack of compliance with the disclosure law troubling.

“A free and fair debate on gambling depends on absolute transparency from these companies,” said James Browning, the group’s regional director of state operations. “It’s important to be able to connect the dots between what they’re giving and the return they’re getting.”

The form is due twice a year from companies doing business with the state as well as those that retain lobbyists in Annapolis. The owners of Maryland Live! and Ocean Downs have employed lobbyists in the capital since at least 2010. Elections officials said they have no record of receiving forms from either casino owner since then.

Some of the information requested on the disclosure form is available in other state filings. But if filled out properly, the form provides more detailed and more timely disclosures than are publicly available elsewhere.

A filing in February, for example, by Penn National Gaming, the owner of a casino in Cecil County, detailed more than $28,000 in campaign contributions late last year and early this year from four affiliated companies, including two in Ohio, to Senate President Thomas V. Mike Miller Jr. (D-Calvert) and other lawmakers.

In Miller’s case, the contributions exceeded what could have been given legally by a single entity.

The spotty disclosure comes amid an effort by Gov. Martin O’Malley (D) and others to rein in the amount of casino money flowing to Maryland candidates.

A provision in the gambling bill introduced by O’Malley during the special session sought to ban casino contributions. The measure was weakened by the legislature, allowing what critics say are several big loopholes. There is nothing in the new law, for example, to prevent companies affiliated with casino owners from making contributions to Maryland candidates.

The new law also does nothing to curb the ability of gambling companies to give unlimited donations to ballot-issue committees. MGM Resorts, which has been lined up to run a proposed casino at National Harbor, has given about $2.4 million to such a committee advocating passage of a statewide ballot measure in November that would allow a gambling venue in Prince George’s County.

The primary focus of the bill passed in the special session was to expand Maryland’s gambling program — pending voter approval — to allow a casino in Prince George’s as well as Las Vegas-style table games, such as blackjack and roulette, at the state’s five previously approved slots sites. Two of those locations have yet to open.

Cordish was the most vocal opponent of the bill during the special session and the weeks of debate that preceded it. The company argued that its Anne Arundel County facility — which opened in June and will soon have 4,750 slot machines — stands to lose a large share of the Washington gambling market if a new casino is allowed in neighboring Prince George’s.

Last month, Maryland Live! generated more than $35 million in slots revenue, about two-thirds of which was retained by the state for education and other programs.

Rickman’s 800-machine casino near Ocean City also had a lot at stake during the special session, and he emerged as one of the clear winners. Lawmakers agreed to bump up the share of slots revenue his facility may retain from 33 percent to 43 percent after hearing about the difficulties of operating in a smaller market.

In a letter to the Maryland State Board of Elections, a lawyer for the owner of Maryland Live! said that the company does not meet the legal definition of “doing business with the state,” which is one of the criteria that would require filing. Penn National Gaming has come to the opposite conclusion regarding its business dealings, based on its filings.

On Wednesday, elections officials requested advice from the Attorney General’s Office as to which interpretation is correct. In either case, casino owners who spend more than $500 on lobbyists are required to fill out the same form.

Jared DeMarinis, the director of candidacy and campaign finance for the elections board, said Wednesday that he would refer the late filing by the owner of Maryland Live! to the State Ethics Commission, as he is required to do by law.

Under Maryland law, it is a misdemeanor to “knowingly and willfully” fail to comply with the disclosure requirement. Violators are subject to a fine of up to $1,000 and a year in prison.