About 3 million more people enrolled in Medicaid or the Children’s Health Insurance Program from October through February, an increase tied to the opening of the Obamacare insurance marketplaces.

Figures released Friday by the Obama administration show that over that five-month period, a total of 11.7 million people were determined eligible for the two programs. Both numbers could rise further once all states finish reporting their data, officials said.

The uptake in Medicaid enrollment was especially driven by states that have expanded the program under the health care law, according to the new figures. Expansion states recorded an 8.3 percent jump in enrollment, while states that did not expand had a 1.6 percent increase.

Agency officials and policy experts noted that the figures are estimates and likely to rise further as states review and update their data.

The biggest change in Medicaid came in Oregon. The state has one of the nation’s worst health exchange websites — which still cannot process an application entirely online — but it is operating a “fast track” program that helped to drive a 34.8 percent spike in Medicaid enrollment from September to February. Oregon is using data from CHIP and the Supplemental Nutrition Assistance Program to quickly enroll people whose income and residency information is already on file.

Other Medicaid expansion states with very high enrollment gains through February include West Virginia (33.5 percent), Vermont (32.3 percent) and Colorado (22.8 percent).

But some non-expansion states also saw relatively large growth in enrollment, including Florida (8.2 percent), Montana (6.9 percent) and Idaho (6.6 percent). In these, the new enrollees are people who had already been eligible for Medicaid but might not have known it. Policy experts call this the “woodwork” or “welcome mat” effect as news and outreach related to the law draw individuals into the program.