trouble

It was a Monday morning when it was recess time, I saw four student going into the science lab and they seems looking around, I thought that the teachers had gave them permission to go into the science lab to collect something, so I ignore them.
Then after a while, there was several loud boom, then green and blue smoke came billowing out from the science lab and I was in fear those four students were still in there. The student then emerges minutes after the explosion. To my horror, only three students came out, one of them had disappeared. I then saw them going back and rescued the fourth student.
In a minute or so, the entire student had evacuated the building and were lining up in the parade square. Some time later, fire engines came and put out the fire and destroy the poisonous gas. After an investigation, the four students had an order from an adult to put those items which are smoke bomb in the school science lab.
It was a Monday morning when it was recess time, I saw f...