By Jim Donovan

PHILADELPHIA (CBS) –– A Samsung executive apologized on Monday as he detailed the results of the company’s investigation into what caused its Galaxy Note 7 smartphones to overheat and catch fire.

Samsung says it began the recall last September and 700 researchers worked to replicate the problems using 200,000 devices and 30,000 batteries.

They concluded the original issue was a design flaw.

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“It caused two parts of the battery to basically come into contact with each other, and short out and that caused overheating,” said Dan Ackerman of CNET. The replacement phones had a problem with how the batteries were welded together. That led to an internal short circuit.

“They went through great pains to point out that in all of their testing, they didn’t find any flaws with the actual design and build of the phone hardware or the software in it. They put all the blame strictly on the batteries and the manufacturers of those batteries,” Ackerman added.

A source tells CBS News, the first battery was supplied by a Samsung company. The second was outsourced and the production problem there was linked to a rapid increase in production to replace all the phones from the initial recall.

In the United States, Samsung received 13 reports of burns and 47 reports of property damage associated with Note 7 phones. There were 96 total reports of overheating batteries.

The U.S. Consumer Product Safety Commission has yet to release results of their investigation into the overheating problems. Samsung has announced an eight point safety check on all its phones from here on out, which it says will exceed industry standards.