If you've been holding on to a Google+ invitation, now may be the time to use it.
After shutting down the Google+ invitation process late last week because of "insane demand" from people eager to try out its new social network, Google once again began to allow new members in last night.
But Google still isn't close to officially launching the site, which is positioned to compete directly with Facebook. An official launch would open Google+ up to everyone.
Dave Besbris, engineering director for Google+, said in a blog post on the site Wednesday night that Google is only re-opening the invitation mechanism for a short time.
"Things are going well with the systems right now, so we feel comfortable enough to open up invites for a brief period," he wrote. "Our goal is to double the user base in the field trial."
Besbris noted that Google is not commenting on how many people have been allowed in to try out Google+.
"I wanted to take a moment to explain why we're growing the system slowly," he added in his post. "First, we want to make sure our infrastructure scales so the service remains fast and reliable. Second, we want to ensure that bugs are fixed while there are still a relatively few people in the field trial."
He warned users not to send out mass invitations. Google is "throttling" invitations, so users are likely to have more success if they only invite a handful of people, he explained.
When Google closed the invitation process last week, people who had already joined the trial were no longer allowed to invite anyone new, and those who had invitations but hadn't yet acted on them were denied access to Google+.
The company said last week that it expects the invitation process to be periodically opened and closed as it works through field trials.
Google has not said when its new social network might officially open to the public.
There has been enough buzz about Google+ that people have been frustrated with the company's slow rollout. Some people have taken advantage of that frustration by trying to sell invitations on eBay.
Sharon Gaudin covers the Internet and Web 2.0, emerging technologies, and desktop and laptop chips for Computerworld. Follow Sharon on Twitter at @sgaudin, or subscribe to Sharon's RSS feed . Her email address is email@example.com.