SAN FRANCISCO, May 24 (Xinhua) -- Apple Inc. has bought a small California-based startup Tueo Health that is developing a mobile app to track asthma symptoms in children, U.S. media reported Friday.

Tueo Health, a tiny startup founded four years ago with fewer than a dozen employees, is working on the mobile app that was designed to pair with commercial breathing sensors to help parents track asthma conditions in children, U.S. media outlet CNBC said.

The mobile monitoring system can alert parents if their children experience symptoms of irregular breathing at night that could imply asthma conditions.

It said it was not known how much Apple had paid for the acquisition of the health-focused company, but the startup had completed a small seed round in 2017 to raise 1.1 million dollars.

Media reports said Apple has been adding more health features to its products including Apple Watch to expand its medical-related portfolio.

Apple CEO Tim Cook told CNBC earlier this year that health care will be "Apple's greatest contribution to mankind" as the U.S tech giant is investing heavily on health technology.

Apple made acquisitions of two other startups dedicated to health care service in 2016 and 2017, respectively.