Site Frozen: Help, Please

I was updating my plug-ins and accidentally closed the window during the process before it was finished. Now whenever I try to access my site or the admin page, I get the following message:
“Briefly unavailable for scheduled maintenance. Check back in a minute.”

As I can’t even access my admin login, I cannot finish updating the plug-ins (the theme is up to date).

What can I do to fix this? Any help is greatly appreciated.