East Windsor — Nearly 18 months after forming an unlikely alliance to fight off the threat of out-of-state competition, the casino-owning Mashantucket Pequot and Mohegan tribes Thursday signed an agreement with this town’s top elected official to build a third Connecticut casino here.

Kevin Brown, the Mohegan chairman; Rodney Butler, the Mashantucket chairman; and Robert Maynard, the East Windsor first selectman, all took up pens prior to a news conference at a town youth center and made it official.

Whether the proposed casino, intended for a site off Exit 45 of Interstate 91, will ever materialize remains something of an unknown.

Also Thursday, the state legislature’s Public Safety and Security Committee scheduled a public hearing March 9 on enabling legislation that would make a third Connecticut casino possible. The committee this week drafted two bills, one of which calls for a competitive bidding process among casino operators and one that would grant the tribes the exclusive right to build the casino.

“It’s my pleasure to partner with the tribal nations on a new beginning,” Maynard said. “We’re proud to be a part of what they’re doing to keep jobs and revenue here.”

Brown, characterizing East Windsor as “a beautiful town with a rich history and hard-working people, the kind of neighbors who look out for each other,” promised to work with the town in planning the proposed casino.

He said the boarded-up Showcase Cinemas building that now occupies the site likely would be torn down and replaced by a new structure that architects have begun designing.

The $300 million project is supposed to protect the tribes’ respective southeastern Connecticut facilities, Foxwoods and Mohegan Sun, from the impact of MGM Springfield, a $950 million resort casino being built in Massachusetts — less than 20 miles from East Windsor.

“MGM will do whatever it can to maximize the return for its shareholders, even if it means crippling a 25-year-old industry in Connecticut,” Butler said. “We’re not going to do that.”

Foxwoods opened in 1992, Mohegan Sun in 1996.

East Windsor’s police chief and its superintendent of schools spoke in support of the casino project, as did the executive director of the local chamber of commerce and representatives of trade unions and the union for Foxwoods’ table-games dealers.

Under the agreement signed Thursday, the tribes would pay East Windsor $3 million no later than 15 months before the casino opens and then about $8.5 million a year thereafter. That includes a $3 million “mitigation” payment on top of local taxes, which are expected to total about $5.5 million.

The Associated Press reported Thursday that Gov. Dannel P. Malloy has asked the state’s attorney general to weigh in on the risks of pursuing legislation that would allow the tribes to operate a state-regulated commercial casino on nontribal land. Foxwoods and Mohegan Sun are considered tribal rather than commercial ventures and are subject to federal regulation and exclusive gaming agreements with the state.

In a letter sent this week, Malloy asked George Jepsen for his opinion on Connecticut's chances of winning a lawsuit if the legislation is challenged on constitutional grounds.

b.hallenbeck@theday.com