Can faulty PCI Bus burn PCI DAQ cards ?

[MogaRaghu]

I have an industrial test equipment that runs 24/7.  This was commissioned in 2019 Nov.   It had an Advantech Industrial PC which had four PCI slots and I had used a PCI-6229 and PCI-6514 in two of them. 

For no obvious reason the cards went up in smoke when the equipment was normally running. Initially I thought its a kind of short circuit or a 24V dc SMPS fault. But all of them checked out fine. And the PC by itself is now booting OK. 

This is highly perplexing and I have sent the PC for a mother board check up.  But just wanted to know if anyone has faced a similar failure and if the PCI Bus can actually fry cards like this ? In fact I use this combination of cards for most of my industrial projects since 2000 and never had even a single failure. 

Any pointers on how this could have happened ?  Attaching images of the fried cards. 

[santo_13]

You didn't describe what is connected on the other side of the card i.e., external components and how the electrical connections are.

[AnalogKid2DigitalMan]

Judging that the majority of damage appears to near the I/O connector and the large amounts of black soot I am guessing high voltage or ground fault emanating from the equipment to which the cards were connected to,

-AK2DM