Apple watches are displayed following an Apple event in San Francisco, California March 9, 2015. [Photo/Agencies]

Apple Watch fans who wish to make a direct purchase at retail stores may have to wait longer as a key component of the Watch made by a Chinese supplier has been found to be defective, the Wall Street Journal reported Wednesday, citing people familiar with the matter.

The component involved is called taptic engine, designed by Apple Inc to produce the sensation of being tapped on the wrist. The engine is one of the key technologies that the company created for it all-new hardware product.

The component supplier AAC Techonologies Holdings Inc is a Shenzhen-based miniature technologies components solution provider. Its Hong Kong-listed shares tumbled 4.1 percent after the news.

After the part's mass production in February, the Watch's reliability testing revealed that some taptic engines supplied by the company started to break down over time, said the newspaper.

However, the source also said that the engines provided by Apple's the other Japan-based Nidec Corp did not have the same problem, and Apple has moved nearly all of the production of this component to Nidec, but it may take time for the producer to increase the production.

The newspaper said that Apple last week asked its suppliers to slow production until June, which surprised them as the tech company had said the inventory was insufficient, according to people familiar with Apple's supply chain.

The tech giant doesn't plan a recall of the sold watches, as it said that there is no indication that the company shipped the watches with the defective problems, according to the newspaper.

AAC office in Shenzhen could not be reached for comment on Thursday morning.

Apple introduced its all-new hardware Apple Watch at the annual launch event in last September, started accepting orders online on April 10, and began shipping watches to customers on April 24.

It is only selling the product online and in select designer boutiques, but not in its own retail stores.

Though Apple gave no sales figures for the Watch, it described the current quarter as off to "an exciting start", according to Reuters. The company's revenue in China surged 71 percent to $16.8 billion in the first quarter, making the market its biggest market behind the US.

Preorders of Apple Watch Edition, the premium version of the wearable - equipped with leather band and gold watch case – was sold out in China in less than an hour. But they will not be delivered until June.