It is reported by NASA on its Twitter page.

It is noted that undocking occurred at 19:15 Moscow time. At that moment, when the American Unity module, from which the ship was detached, flew over the Pacific Ocean.

Departure confirmed! @ NorthropGrumman's #Cygnus cargo spacecraft was released from the @Space_Station at 12:15 pm ET as our orbiting laboratory was flying 260 miles over the Pacific Ocean. Watch: https://t.co/mzKW5uDsTi Ask questions using # askNASApic.twitter.com / gTjfjUSsVm

- NASA (@NASA) August 6, 2019

The Cygnus spacecraft launched on the Antares rocket from the Virginia Cosmodrome in April. After successfully entering orbit, it delivered 3.5 tons of payload to the ISS.