Days before the launch of President Barack Obama's online health insurance marketplace, government officials and contractors tested a key part of the website to see whether it could handle tens of thousands of consumer users at the same time. It crashed after a simulation in which just a few hundred people tried to log on simultaneously.

Despite the failed test, federal health officials plowed ahead.

When the website went live Oct. 1, it locked up shortly after midnight as about 2,000 users attempted to complete the first step, according to two people familiar with the project.