The Obama administration on Tuesday reported a big increase in new customers signing up for health insurance in Florida, Texas and other states using the federal insurance marketplace.

But in states running their own insurance exchanges, the numbers were more modest.

All told, the administration said, in the first month of open enrollment for 2015 coverage, more than four million people signed up for the first time or re-enrolled through the federal and state insurance marketplaces. About 3.4 million of them were in the 37 states using HealthCare.gov, the website of the federal marketplace.

More than two million consumers signed up for the first time, the administration reported, and 1.8 million of them did so through the federal marketplace. States with large numbers of new customers in the federal exchange included Florida (330,000), Texas (205,000), North Carolina (110,000), Georgia (103,000) and Pennsylvania (95,000).

The report showed the importance of subsidies to people seeking coverage under the Affordable Care Act.

Officials said that 87 percent of those selecting health plans for next year in the federal exchange had qualified for subsidies that would reduce their premiums. That is larger than the proportion of people who qualified for financial assistance in the initial months of the first open enrollment period (80 percent from October to December 2013). But it is about the same as the proportion who eventually qualified for subsidies in the federal exchange: 86 percent through March 2014.