Samsung announced the recall of Galaxy Note 7 smartphones last month, as the phones came with a faulty battery that caused them to catch fire while charging. The South Korean company has replaced most of the 2.5 million Note 7 units that it sold before it launched the product replacement program.

Replaced Galaxy Note 7 units might not be as safe as Samsung officials claim, as a recent incident may force the company to change its strategy yet again. A replaced Galaxy Note 7 smartphone caught fire on an airplane, causing the evacuation of all passengers and crew.

The CPSC is currently investigating the issue and Samsung might be forced to launch a new recall of its latest flagship. There are also some reports saying that US carriers will allow customers to swap replaced Note 7 units with any other phone. Meanwhile, the Applied Energy Hub battery laboratory in Singapore conducted a battery test on a Galaxy Note 7 smartphone, according to The Telegraph.

The Galaxy Note 7 unit went up in flames

Researchers applied pressure on a fully charged Note 7 smartphone to determine the moment when it would start combusting. They gradually increased the pressure and when the limit was reached, the smartphone went up in flames. Images show how the device catches fire and burns almost completely. It’s unclear if the device was a recalled or replaced unit.

However, any device carrying a lithium-ion battery could face the same fate when enough pressure is applied. Such batteries are known for going up in flames when internal components come in contact after the battery was punctured.

The pictures show a burnt Note 7 smartphone that’s similar to previous reports of such smartphones catching fire. The battery is completely burnt, as the flame was big enough to reach the machine that applied the pressure.