Police are investigating two armed robberies of Metro PCS cellphone stores in Nassau County on the same day.

Investigators believe the Friday robberies -- one in Valley Stream, the other in Hempstead -- are not related, police said.

advertisement | advertise on newsday

At 7:10 p.m. in Valley Stream, an unknown man walked into Metro PCS at 200 W. Merrick Rd., where he placed a plastic shopping bag on the counter, displayed a black semi-automatic handgun, and demanded money from a store employee, police said Saturday in a news release.

The victim, a woman, 29, handed over an undetermined sum of cash, police said. The man fled north on foot along Ballard Avenue. He is described by police as 5 feet, 9 inches tall, in his 20s, blue eyes, reddish beard, and wearing jeans and a gray hooded sweatshirt.

In what police said is an unrelated robbery earlier in the day around noon in Hempstead, another man armed with a black handgun demanded money from a 19-year-old female clerk at a Metro PCS at 652 Fulton St.

The suspect in that robbery was wearing a gray hooded sweatshirt, black jeans, black baseball cap and black sneakers. He fled east on Fulton Street with an undisclosed amount of money. No injuries were reported.

advertisement | advertise on newsday

The Major Case Bureau is investigating. Anyone with information on either of these crimes is asked to call Nassau County Crime Stoppers at 1-800-224-TIPS. All calls will be kept confidential.