Roughly one fourth of this growth was from new plans, including new insurers and CO-OP plans as well as insurers that had previously operated in other markets or states, Kaiser said.

“This first look at the direction of enrollment suggests that, even accounting for people leaving the market, the number of people purchasing their own health coverage grew substantially and likely continued to grow toward the end of the enrollment period,” Kaiser reported.

Kaiser analyzed carrier reports to state regulators. The number of individual plan sales could be much higher, Kaiser said, because filings only represent the number of people whose coverage began by March 31. Additionally, Kaiser said, some larger carriers haven't yet filed their 2014 data.

“Assuming the off-exchange market experienced a surge similar to the state marketplaces,” the net increase in individual market enrollment could ultimately be twice as large, once the next round of data becomes available, Kaiser said.

However, in its report Kaiser acknowledged that “many questions remain and we will need to wait for the next round of filings to get a more complete picture of overall enrollment, including capturing the late March enrollment surge.”

The administration said 8.1 million people have signed up for coverage through PPACA's exchanges as of April.