BERLIN (AP) — Investigators are looking into suspicions of unauthorized entry and possible tampering with the water supply at a major air force barracks in western Germany, authorities said Wednesday.

Defense Ministry spokesperson Arne Collatz said there were suspicions of attempted or actual illegal entry, as well as sabotage, at the Wahn barracks outside Cologne.

A hole was found overnight in the fence of the facility in an area near its waterworks, and officials couldn't rule out contamination, military spokesperson Ulrich Fonrobert said. The barracks was sealed off for several hours in case a perpetrator or perpetrators were on the grounds, but none was found and the gates were reopened Wednesday lunchtime.

Speaking outside the barracks, Fonrobert said the alarm had been triggered by a report of “abnormal water values,” on which he didn't elaborate. An evaluation of the facility's drinking water was still ongoing.

Officials weren't aware of anyone having been sickened by any possible contamination. Fonrobert said that one person reported sick with a stomach bug, but that happened early Tuesday evening and was unlinked to the water supply.

The barracks serves the military part of Cologne/Bonn Airport, where the fleet of military aircraft that serves the German government has its main base.