SAN FRANCISCO – WhatsApp is testing a system that would let business talk directly to Whatsapp users for the first time, Dunya news reported.

The tests, which are being carried out with a handful of companies that are part of the Y Combinator startup incubator, are an important indication of how WhatsApp plans to make money from its massively popular service. WhatsApp has not introduced a business model in the three years since Facebook Inc bought it for a hefty $19 billion.

 WhatsApp, a pun on the phrase “What s up?”, has helped to upend mobile services by enabling users to text or call friends and family for free, without text message charges. It competes with similar services such as WeChat, a unit of China s Tencent Holdings Ltd.

One potential revenue source is to charge businesses that want to contact customers on WhatsApp. But the company is working carefully to avoid problems with spam messages, the documents show.

WhatsApp is also surveying users about the extent to which they talk to businesses on WhatsApp, and whether they have ever received spam, according to the documents.

WhatsApp last year announced its plan to develop the system, known as an application programing interface, or API, citing examples such as a user talking to a bank about a fraudulent transaction or to an airline about a delayed flight.

Last month WhatsApp struck a deal with Y Combinator, which provides training and advice to startups that show potential, to have a small number of companies take part in an early trial, according to emails and messages posted on a Y Combinator forum.

Admission to Y Combinator, founded in 2005, is highly competitive, and past participants include such companies as Airbnb and Dropbox.

A WhatsApp spokeswoman declined to comment on the testing of the system.

Y Combinator President Sam Altman said in an email he was not aware of the WhatsApp test but added: “We do generally see a lot of companies wanting to test their products with YC cos.”