Phone service was restored to Scott Air Force Base and Memorial Hospital at about 1:25 p.m. Friday after it went out earlier in the day for unknown reasons.
"It's been restored," said Scott Morris, spokesman for Windstream Communications. "But we're doing a full investigation about what caused the problem in the first place."
Morris said the malfunction is believed to have originated in Collinsville where Windstream's local lines connect with the AT&T network.
All morning Friday calls to the hospital were met by silence after the phone number was entered. Calls to and from the base were met by a busy signal.
An AT&T spokeswoman said that company's infrastructure was working normally throughout the day.
"I've checked with all our local resources and everyone has indicated that our network in Belleville is operating normally," Katie Nagus, spokeswoman for AT&T in St. Louis, said Friday morning. "If there was a line cut, we'd definitely know about it."
Scott Air Force workers reported that long distance calls could be made while the system was down. But local calls wouldn't go through.
Morris said, he couldn't pinpoint as of Friday afternoon whether the problem was computer-related or a hardware issue.
Contact reporter Scott Wuerz at firstname.lastname@example.org or call 239-2626.