As the investigation into the huge Safeway fire continues, we have been looking at the kind of roof the store had, and whether the monsoon storm might have been too much for it.

A flat roof is not problematic in general -- remember, just about any store or industrial building has one.

[VIDEO: Phoenix Safeway grocery store gutted by ginormous 3-alarm fire]

Story Continues Below

But if not maintained, a flat roof could literally buckle beneath the weight of stormwater.

Arizona's Family showed you live images of portions of the Safeway at 35th and Northern avenues collapsing in, and now firefighters think the monsoon storm may have been to blame. There was a downpour of rain, a collapsed roof which likely broke a gas line and destroyed an electric box.

[READ MORE: Phoenix FD gives possible cause for massive fire at Safeway]

Story Continues Below

“If we have a lake in this parking lot, if the roof had that same amount of weight that that water creates on that roof is overwhelming," Phoenix Fire Capt. Rob McDade said during the firefight on Wednesday.

[READ MORE: 'It was like a haboob': Huge fire rips through Safeway in west Phoenix]

The roof itself is something that needs attention in monsoon season. Rain can quickly become the enemy to flat roofs – or nearly flat roofs. Even some homes in the Valley have flat roofs. Structural engineer Hadi Islam says they are designed to balance the natural, gravitational sag of the material with the added weight of pooling water when it rains.

Story Continues Below

[SLIDESHOW: Massive fire rips through west Phoenix Safeway]

"For some reason, if it is the storm or something like the leaves or some debris is gonna clog, then it’s going to pond more and more. And that is not designed for that," Islam said.

[RAW VIDEO: Safeway sign collapses during massive fire at west Phoenix store]

And that’s the key. If scuppers – the drains that direct water back to the ground – aren’t maintained, the roof is going to end up dealing with way more water than it should. So anyone with a flat roof should head up there from time to time, especially when you know a storm is coming.

"Check all the drains are clean before it comes occasionally – I would say periodically – that all the drains are clean," Islam said.

[SPECIAL SECTION: Arizona monsoon in 2018]

And it’s not just overhanging trees that drop leaves into the drains. Even garbage on the ground can get swept up by the wind and eventually clog a drain on the roof.

Click/tap here to download the free azfamily mobile app.

Copyright 2018 KPHO/KTVK (KPHO Broadcasting Corporation). All rights reserved.