(CNN) The demand to buy US Series I savings bonds this week has been so great that it temporarily crashed the Treasury web site where those bonds are purchased. That could mean some investors’ requests may not be processed in time to lock in the bond’s 9.62% rate by the October 28 deadline.

TreasuryDirect.gov was alerting users to that possibility on Thursday, citing “unprecedented” volumes. “We cannot guarantee that your bond purchase will be completed before this deadline if your account or purchase requires additional customer support for issues such as identity verification.”

Treasury said Thursday it has since fixed the underlying technical issues and has more than doubled the connectivity capacity of the site to allow more customers to successfully set up accounts and purchase bonds. But, a Treasury official noted, there might still be some intermittent issues depending on traffic in the next two days.

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