WASHINGTON — The Obama administration said Tuesday that 1.46 million people had applied and been found eligible for Medicaid or the Children’s Health Insurance Program in October, far more than had selected a private health plan in the new insurance marketplaces.

Of those found eligible for the Medicaid or CHIP, slightly more than half were in states that have decided to expand Medicaid, as permitted under the Affordable Care Act.

But 48 percent of the people found eligible for the programs — 697,000 people — were in states that have not expanded Medicaid.

The new health care law has produced many changes in the way states assess eligibility for Medicaid, and it provided money to states to upgrade antiquated computer systems. These changes, combined with publicity around the rollout of the federal law this fall, apparently contributed to increases in the number of applications for Medicaid and in the number approved.

“In October, in states that are fully participating in the expansion of Medicaid coverage made possible by the law, we’ve seen a more than 15 percent jump in applications compared with the average monthly enrollment in July through September,’’ the Department of Health and Human Services said. “This shows a real need and desire for coverage for low-income Americans.’’

The report confirms expectations that many people who were eligible for Medicaid but not enrolled would come forward and seek coverage, even in states not expanding Medicaid.

For example, about 370,000 people were found eligible for Medicaid or CHIP last month in four states that have not expanded Medicaid: Florida (165,000), North Carolina (59,000), Pennsylvania (72,500) and South Carolina (73,300).

By contrast, in October, just 26,800 people selected private health plans in the new federal exchange, and 79,400 chose private plans through exchanges run by states.

States have decades of experience running Medicaid and carrying out changes in eligibility. In addition, since Medicaid is one of the biggest programs in state budgets, state Medicaid directors are often skilled, experienced managers, and their operation of the program is closely supervised by governors in almost every state.

The insurance exchanges, on the other hand, are entirely new, as are the computer systems, and congressional investigators have found huge deficiencies in management of the federal exchange.