It seems it's mission changes between films. In the first they were involved in biohazard weapons and sent in a sway team to clean up the mess.

Two they tried containing it in Raccoon city and were investigating what went down there. So who was sent to clean it up? They must've known by the time they sent two swat teams in and if the zombies were a mystery only discovered when they opened the hive who reported it?

They were attacked upon the doors opening and wouldn't really have time to tell anyone. Heck, even the press were able to report it by early morning before the corporation knew?