During the first month of open enrollment, more than 36,000 Mainers signed up for health insurance through the Affordable Care Act marketplace.

According to a report released Tuesday by the federal Department of Health and Human Services, 61 percent of those people re-enrolled in a marketplace plan, while 39 percent used the marketplace at Healthcare.gov for the first time. Eighty-nine percent of those Mainers were eligible for a federal subsidy.

The report is the first to analyze marketplace enrollment for 2015. It looked at enrollment in Maine from Nov. 15 through Dec. 15, the last day people could sign up for insurance to start on Jan. 1.

ACA advocates called the numbers “encouraging.”

“About as many people were deemed eligible in that first month of open enrollment as signed up during the whole year last year,” said Jacob Grindle, program coordinator for Western Maine Community Action, one of two Maine organizations that received federal money to help Mainers sign up through the marketplace.

More than 40,000 Mainers signed up through the marketplace this past year. According to a projection by the Urban Institute and the Robert Wood Johnson Foundation, that figure could more than double to 82,000 by the end of open enrollment in 2016.

Experts believe enrollment figures already have increased. That’s because automatic re-enrollment started on Dec. 16, a day after the report ended its analysis. Mainers who did nothing and allowed their plans to auto renew were not included in this count.

Considering the number of people who signed up in 2014 and the number who actively re-enrolled, Grindle estimates 15,000 Mainers allowed their plans to automatically renew.

“I think there are probably 60,000 people who are probably going to have coverage come Jan. 1,” he said.

Grindle called that “a really good number.” And not surprising based on his group’s experience helping people sign up this past month.

“We got very, very swamped with phone calls,” he said. “We booked up before Dec. 15 a couple of weeks ahead of time.”

Other ACA advocates were pleased with the report.

“I think the numbers are really encouraging, given that we’re only a third of the way through the enrollment period,” said Mitchell Stein, a Maine health policy consultant who supports the ACA.

Open enrollment ends Feb. 15.

They also lauded the high number of Mainers — 61 percent — who actively re-enrolled rather than doing nothing and allowing their plan to automatically renew. Experts, advocates and insurance groups urged Mainers to review their insurance options so they weren’t placed into a plan that was no longer a good fit.

“I think a lot of people have gotten that message,” Stein said.

Those groups now have a new message: Open enrollment ends soon.

“Our focus for the second half of open enrollment is to encourage people not to wait,” said Emily Brostek, head of Consumers for Affordable Health Care.

Bangor Daily News Health Editor Jackie Farwell contributed to this report.