Massachusetts State Police troopers have seized thousands of firecrackers in a pre-Fourth of July operation targeting the illegal importation of fireworks from out of state.Troopers first discussed the operation on Monday, when they announced the seizure of fireworks worth more than $28,000 over the three previous days. At that time, 18 people were issued a summons for the charge of illegal possession of fireworks.As of Friday morning, the number of people summonsed for the same charge had grown to more than 30, state police said. Megan Kearns, manager of Phantom Fireworks in Seabrook, New Hampshire, said she saw several Massachusetts State Police officials taping video of customers and vehicles in the store's parking lot over the weekend. Kearns said it was the most extensive surveillance she has seen in approximately a decade."We haven't seen any blowback from that here. I mean, we have lots of customers who are happy when they come in and they're happy when they leave," Kearns said. Fireworks are legal in New Hampshire but in 2020, Phantom Fireworks was ordered by the Massachusetts Attorney General to stop mailing advertisements across the border. Under state law, it is illegal to use, possess or sell fireworks in Massachusetts. It is also illegal to buy them elsewhere and bring them into the state.This ban includes sparklers, which burn hot enough to melt glass, officials point out."There were 944 fires and explosions involving illegal fireworks in Massachusetts in the past 10 years," according to the Massachusetts Department of Fire Services. "These incidents caused three civilian injuries, 43 fire service injuries, and millions of dollars in damages."While individuals are not allowed to possess or use fireworks, professionals are granted permits to conduct public shows. Dozens of fireworks shows are scheduled in Massachusetts through mid-July.