More than 3 million Americans have enrolled in Medicaid and the Children’s Health Insurance Program since October, according to data released Friday, providing the first enrollment snapshot of the government-run programs for low-income people since the health insurance marketplaces opened.

As of Feb. 28, Medicaid and CHIP enrollment has grown to 61 million in 46 states that reported the data, 3 million higher than enrollment was, on average, from July to September, the data show. Administration officials had previously provided numbers only for those determined eligible for the programs.

White House officials pointed to the data as growing evidence that more people are gaining coverage as a result of the Affordable Care Act. This week, the White House announced that 7.1 million people had signed up for health coverage as of March 31 on the marketplaces, marking a turnaround from the troubled beginnings of enrollment last fall.

The health law expanded Medicaid to include all legal residents with incomes less than 138 percent of the federal poverty level or individuals making less than about $15,800 a year or a family of four earning less than $32,499 in 2013 dollars. That includes childless adults, who were excluded in most states despite a widely held misperception that all poor people automatically qualified for Medicaid.

But after the U.S. Supreme Court ruled in 2012 that states could not be compelled to expand their programs, many states refused to participate. In 24 states and the District of Columbia, millions of low-income adults became newly eligible for Medicaid as of January 2014. On April 1, Michigan expanded its Medicaid program under the law, and New Hampshire will expand starting in July.

Health and Human Services Secretary Kathleen Sebelius noted in a blog post Friday that states that have expanded Medicaid had a “much more dramatic increase” in enrollment than states that have not. Medicaid enrollment in the expansion states grew 8.3 percent since September, five times more than non-expansion states, which had a 1.6 percent increase during the same period, she said.

“The increase in Medicaid enrollments across the country is encouraging, but more work is left to do to ensure that the millions of uninsured Americans eligible for these programs gain coverage,” Sebelius said.

“This is a clearer picture of what is happening to total enrollment, ” said Robin Rudowitz, a policy analyst at the Kaiser Family Foundation.

But the data released Friday by the Centers for Medicare and Medicaid Services (CMS) do not answer a key question.

“In the expansion states, what we don’t know, of these 3 million, how many are directly attributable to the expansion versus people who were eligible previously and have now enrolled because of increased awareness associated with the Affordable Care Act?” said Elizabeth Carpenter, a policy analyst with Avalere Health, a consulting firm that has been monitoring enrollment.

Federal officials say the latest numbers underestimate the program’s growth because not all states reported Medicaid enrollment. In addition, the totals do not include people who will later be found eligible for Medicaid coverage retroactive to February. The totals also do not include sign-ups for March, when state and federal insurance marketplaces had a tremendous surge of people seeking coverage.

The Congressional Budget Office estimated that 8 million people would be added to Medicaid in 2014. Unlike sign-ups for private insurance on the marketplaces, which closed March 31, enrollment in Medicaid continues year-round. Administration officials said they plan to continue outreach efforts and effective strategies such as partnering with hospitals to make preliminary eligibility determinations and using food stamp data to find people who are likely to be eligible for Medicaid and CHIP.

Even among the states that expanded Medicaid, enrollment data released Friday show a wide variation across the country. In Oregon, enrollment jumped almost 35 percent, while Arizona’s increase was closer to 3 percent. States that showed more than 10 percent enrollment increases were Arkansas (12 percent), Colorado (22 percent) and West Virginia (33.5 percent).

In the states that did not expand Medicaid, Florida had the biggest increase — 8.2 percent. Montana ranked second with a 6.9 percent increase, and Idaho was third with a 6.6 percent jump.

From October to February, states reported that 11.7 million people were found to be eligible for Medicaid and CHIP, according to CMS.

Friday’s data showing 3 million additional individuals had enrolled during that period reflects several factors:

●Enrollment only includes people eligible for full coverage, while eligibility includes people receiving limited benefits.

●Some of the eligibility figures may include duplicates, while the enrollment numbers do not.

●Some individuals determined eligible for Medicaid may have found coverage elsewhere.

The report does not include all the people who signed up for Medicaid through HealthCare.gov, the federal exchange serving 36 states, because of earlier problems transferring those applications to the states.