Casino opponents are seeking a recount in last week’s election, in which Mainers approved the state’s first casino with both table games and slot machines.

Petitions with more than 150 signatures were delivered to the Secretary of State’s Office in Augusta before Tuesday’s 5 p.m. deadline.

Voters approved a ballot question on Nov. 2 to allow a casino in the western Maine town of Oxford by fewer than 5,300 votes — less than 1 percentage point out of more than 556,000 votes, according to unofficial tallies.

“The margin was so close and so many people worked so hard for so long, we felt obligated to all the supporters to make sure we did in fact lose it at the polls,” said Scott Vlaun of Oxford Hills No on One, an anti-casino group. “It seems, at that range, there’s plenty of room for error.”

Rob Lally, one of the casino investors with Black Bear Entertainment LLC, said he’s confident the vote will be upheld.

“With the numbers we’ve won by, it will be very unlikely this will be overturned or changed,” he said.

Black Bear Entertainment is proposing a $165 million resort that will be built in phases and include a casino, a 200-room hotel, restaurants, convention space and a spa. The project would be along Route 26, though the exact location hasn’t been made public.

Maine now has one casino, Hollywood Slots in Bangor, which has 1,000 slot machines but is prohibited by law from having table games such as blackjack and craps.

Supporters of the project in Oxford say it would provide jobs, jump-start the local economy and generate tens of millions of dollars in tax revenue each year. Critics say it would suck jobs out of the local economy while creating other problems, such as increased crime and gambling addiction.

Vlaun said the Oxford Hills No on One group is working with the CasinosNo! organization in the recount effort. A third casino opposition group, Citizens Against the Oxford Casino, said it is not seeking a recount.

Dennis Bailey of CasinosNo! said the recount request is a “precautionary” move, just in case more ballots turn up or discrepancies are discovered in the vote counts.

At least 100 signatures have to be certified for the recount to move forward, said Secretary of State Matthew Dunlap.

After the signatures are certified, all ballots cast statewide will be delivered to Augusta, where they will be counted by supporters and opponents of the proposal under the supervision of state election officials.

Given the large number of ballots, a recount would probably take as long as four weeks, Dunlap said.

The last recount on a statewide ballot measure came after a referendum in 1995, in which voters approved a mandatory seat belt law by less than 1 percentage point. The recount was halted after less than 12 percent of the ballots had been recounted, when the opposing group said it was satisfied with the results.

In 1970, the gubernatorial election victory of Kenneth Curtis withstood a recount after he won by 890 of about 325,000 votes cast.