WASHINGTON — The head of the U.S. government’s personnel office is rejecting bipartisan calls for her resignation following revelations that hackers stole the personal information of more than 21 million people on her watch.

Katherine Archuleta, director of the federal Office of Personnel Management, said she has no plans to step down and is committed to continuing her work. The White House, which had previously said President Barack Obama was confident in Archuleta’s leadership, said there was no change in its position.

The escalating calls for Archuleta to be replaced came as the Obama administration disclosed on Thursday that the number of people affected by the federal breach — believed to be the biggest in U.S. history — was far higher than previously reported.

Hackers downloaded Social Security numbers, health histories or other highly sensitive data from OPM’s databases, affecting more than five times the 4.2 million people the government first disclosed this year. Since then, the administration acknowledged a second, related breach of systems housing private data that individuals submit during background investigations to obtain security clearances.

Although the government declined to name the hackers, officials said the same party was responsible for both hacks. Numerous U.S. lawmakers who have been briefed on the federal investigation have pointed the finger at China.