Palo Alto police are investigating two robberies involving pedestrians that occurred within 15 hours of one another, they said in statements released Tuesday.

At 1 a.m. on March 15, a man in his 30s was robbed in the 300 block of University Avenue by two men who approached him while he was walking. The men told him to empty his pockets. One of the men lifted his sweatshirt to display a black handgun in the waistband of his pants.

The man gave them the contents of his pockets and backpack. One of the thieves took the man's laptop out of the backpack but returned it after the victim said it was a "work" laptop. The other man took the pedestrian's cellphone but returned it after his partner told him not to take it. The duo kept two of the man's credit cards and walked east on University Avenue, according to police.

Officers were not able to locate the two men, who were both wearing hooded sweatshirts and face coverings. One was about 5 feet, 10 inches tall; the other was about 5 feet, 8 inches tall.

Police are also investigating another robbery that occurred 15 hours earlier at about 9:40 a.m. on March 14. In this case, two men ran past a woman in her 40s walking on a sidewalk in the 2000 block of Webster Street and stole a cellphone out of her hand.

The woman told police she was talking on her cellphone when she noticed two men walking behind her for a couple of minutes. She then heard them running toward her, and one of the men grabbed her phone as they passed her.

They ran across the street to a white four-door sedan that had been parked around the corner and got in the passenger side of the car. The car drove west on Santa Rita Avenue. The woman ran back to her home and called the police.

The duo was described as teenage boys who were both about 5 feet, 9 inches tall and wore face coverings. One wore a red hooded sweatshirt with white lettering; the other wore a black hooded sweatshirt. She did not see the driver of the getaway vehicle.

Police are actively investigating both robberies and whether they are connected. As of late Tuesday morning, detectives have no evidence directly linking the two cases and suspect they are not related.

Anyone with information is asked to call Palo Alto Police Department's 24-hour dispatch center at 650-329-2413. Anonymous tips can be emailed to [email protected] or sent by text message or voicemail to 650-383-8984.