While checking for the source of the leak, check the drains in that area. The whole reason for the leak could be a backed up, plugged drain. The water flowing over the flashings is a leak that is easily repaired by cleaning the drain. This should be done as part of the facility's normal roof maintenance program, however, sometimes between routine maintenance checks debris and other objects accumulate on the roof clogging up the drain system. Look for missing or displaced metal from fan housings, ducts and access doors.
Notification Check the roofing file to find out which roofer installed the roof.
If it is under five years then it may be something for which the contractor is still responsible, but most contractors do not give warranties beyond one or two years. If there is a manufacturer warranty, immediately notify the manufacturer directly. The roofer may be responsible to do some of the repair work, but make sure the manufacturer knows that the roof has a leak and that you are very interested in repairing the leak as quickly as possible. You may consider trying to stop the leak yourself particularly if more rain is predicted. If the roofing contractor says he can have someone there right away then let him.