Posted by: Stefanie Boe, KOLD News 13 This Morning Senior Producer

It's happened again in Phoenix--mystery lights over the city. Monday night, police and local media outlets received hundreds of calls after people spotted four or five red colored lights in the sky.

Callers said the lights were over north Phoenix and appeared at one point in a straight line, and also formed a square and then a triangle.

According to www.azcentral.com the lights were visible for about 15 minutes around 8 p.m. before heading to the east and disappearing.

No one seems to have an explanation for the lights. The Air Force says they were not part of any Air Force activities.

Back in March of 1997 thousands of people saw lights over the Phoenix-area. In that instance they were white and shaped like a "v".