[Zope] timeout on external methods?

I have a page in Zope which calls a Perl script via an External Method. The perl script takes a long time to complete -- about 8 minutes. After exactly 5 minutes, I see a second perl process launched by Zope. At 8 minutes, the first perl process completes, but I do not see the response in my browser. After 10 minutes, I get "This page cannot be displayed" in my browser, but the second perl process is still running. Does Zope have a timeout that is causing it to re-try the perl script after 5 minutes? Is this adjustable?