Samsung has delayed shipments of its latest flagship smartphone, the Galaxy Note 7, as it conducts additional quality control testing.

Local news agency Yonhap reported that deliveries from the Korean electronics firm to three of South Korea’s mobile phone networks, SK Telecom, KT and LG Uplus, which began at the beginning of this week, were halted unexpectedly.

A Samsung spokesperson told Reuters: “Shipments of the Galaxy Note 7 are being delayed due to additional tests being conducted for product quality.”

There have been several unconfirmed local reports of users claiming that the battery of the Galaxy Note 7 exploded during charging. Samsung did not elaborate on what further testing was required and to where shipments of the high-priced phablet were being delayed.

The Galaxy Note 7 is the first Samsung smartphone to have a USB-C connector. The new connector brings with it a new charging standard to which some third-party cables have been found to be non-compliant, causing damage to devices from laptops to smartphones using the new port. Amazon recentlyclamped down on the non-compliant and dangerous cables.

Quality-control problems delaying the release of the latest Samsung flagship phablet could be a major blow for the world’s largest smartphone manufacturer. Its recent sales saw it capture more market share and return to solid profits, but high sales of the Note 7 along with the Galaxy S7 line are required to maintain momentum in the second half of the year.

The company has previously said that demand for the Note 7, which marks the first return to Europe for the phablet line since 2014’s Note 4, has far outstripped supply, forcing the launch of the smartphone to be pushed back in some markets.

Production problems for the curved-screen Galaxy S6 Edge last year resulted in poorer than expected sales in some regions. Samsung will be hoping to avoid a repeat of the problems with the Note 7, which has garnered favourable reviews and is expected to sell double that of previous versions.