Measures were taken to restore the site, they said.
Pakistanis overwhelmed the website after the commission published nomination papers for all candidates running in the country's upcoming general election, Geo News reported Monday.
Officials decided to temporarily shut down the site to prevent any possible loss.
All candidates in the general election were required by the commission and Pakistan's Supreme Court to provide citizens with copies of their nomination papers.
The Supreme Court required the commission to publish the papers online.