Los Angeles police late Friday were on citywide tactical alert after a wave of smash-and-grab “flash mob” robberies at high-end stores.

And in Lakewood, Los Angeles County Sheriff’s Department detectives were investigating a possible smash-and-grab robbery at a Home Depot after people stormed into the store Friday night and fled with sledgehammers and bolt cutters, according to authorities and a store employee.

The Los Angeles Police Department declared the alert around 8:30 p.m. Friday and lifted it at 2 a.m. Saturday. The alert followed a string of robberies in the area early in the evening, including an incident at 5:30 p.m. in which at least 10 men robbed a store at 130 S. La Brea Ave., pushed employees onto the ground and fled, said LAPD Officer Mike Lopez.

Lopez said that another attempted robbery on La Brea Avenue around 5:30 p.m. ended with an employee being sprayed with some kind of chemical agent, and another robbery was carried out at gunpoint in the 7800 block of Melrose Avenue.

Los Angeles police also took three people into custody Friday afternoon in the area of Melrose Avenue and Gardner Street after pulling over a vehicle for a traffic violation and spotting clothing with security tags “in plain sight,” connected to another theft, Lopez said.

Friday’s tactical alert follows a series of robberies in which groups have swooped in on stores across Los Angeles — including a Nordstrom at the Grove shopping center and several stores at the Beverly Center in the Beverly Grove neighborhood — and fled with thousands of dollars in merchandise.

Three people have been arrested in connection with the incident at Nordstrom on Tuesday, where as many as 20 people stole $5,000 worth of merchandise after smashing a display window, police said.

In Canoga Park, several people entered a Nordstrom store Wednesday night at the Westfield Topanga & the Village shopping center, where they attacked a security guard with bear spray and took off with merchandise.

In Lakewood on Friday, approximately eight people entered a Home Depot shortly before 8 p.m. and stole roughly $400 worth of hammers, sledgehammers and crowbars, according to the sheriff’s department.

“Witnesses saw multiple vehicles taking off,” Deputy Miguel Meza said.

A store employee told The Times in a phone interview that men took sledgehammers and crowbars and some wore sweatshirts with hoodies.

The Beverly Hills Police Department said early Saturday that it had arrested four suspects who might be tied to the Home Depot robbery being investigated by the Los Angeles County Sheriff’s Department. Beverly Hills police said that just after 9 p.m. Friday, they had stopped two cars after getting a call from an “alert citizen” reporting that six vehicles were driving around the Beverly Hills business district without license plates.

The two cars stopped by police were occupied by several men and two babies, according to the department. No crimes in Beverly Hills had been linked to the four adults who were arrested, Beverly Hills police said Saturday.