FREMONT — A liquor store and restaurant were robbed at gunpoint and five businesses were broken into during a series of unrelated crimes that kept police busy on Friday and over the weekend.

Authorities on Monday said they were still investigating the crimes, and noted that no one had been arrested.

Although some of the crimes were similar in nature, most appeared to be unrelated, said Sgt. Chris Mazzone, a spokesman for the Police Department.

Both of the armed robberies happened Friday, the first at 1 p.m. at Irvington Liquors on Fremont Boulevard near Irvington Avenue, and the second just before 11 p.m. at Little Caesar's Pizza on Fremont Boulevard near Sundale Avenue.

In the liquor store heist, two armed men entered the store and held a teenage boy at gunpoint while forcing his mother — the clerk — to hand over cash from the register, Mazzone said.

The assailants, who were described as light-skinned men wearing black clothing and bandannas over their faces, put money into a black backpack and were last seen running toward the nearby carwash, the sergeant said.

Later that evening, police were dispatched to the pizza restaurant, where two men also armed with guns robbed the business of money from the register.

Witnesses said the thieves — who were described as dark-skinned men in dark-colored clothing — busted the register open and took cash. The assailants were last seen fleeing toward the nearby Waterstone Apartments, Mazzone said.

Two days later, police responded to five instances in which businesses had their windows smashed or doors kicked in either by vandals or would-be burglars, Mazzone said.

Three of them happened at a shopping complex on Towers Way near Thornton Avenue early Sunday, the sergeant said.

Three of the businesses — an Islamic center, a restaurant and a mini market — share a common corridor that was enclosed by glass windows and a door.

That area was initially broken into sometime before 8 a.m. Once inside, the culprits broke open doors of the three businesses but apparently didn't take anything, Mazzone said.

In the other two cases, police said a pizza restaurant on Fremont Boulevard near Eggers Drive had its window smashed — but nothing was stolen — and a hardware supply store on Hannover Place was burglarized.

The same day, four thieves apparently broke into Grainger Industrial Supply about 8 a.m. and made off with several power tools before police arrived.

Anyone with information about any of the crimes may call police at 510-790-6900.

Contact Ben Aguirre Jr. at 510-353-7011. Follow him at Twitter.com/benaguirrejr.