BOSTON (AP) – Attorney General Thomas F. Reilly will investigate all reports of stores that opened illegally on Thanksgiving Day, as several Boston-area supermarkets defied a centuries old law and welcomed shoppers.

“Every employer should know the law,” David Guarino, Reilly’s spokesman, told The Boston Globe. “If these stores want to open, there’s a way to do it: Change the law.”

The law enforced by Reilly is part of the so-called Massachusetts Blue Laws. Many of the Puritan-era laws, passed in the 1600s to keep colonists at home or in church on Sundays, have been repealed, such as a ban of liquor sales on Sundays.

But one that remains in effect requires all stores, except convenience stores and gas stations, to close on Thanksgiving, Christmas and New Year’s Day.

Last week, Reilly’s office told the Whole Foods supermarkets chain it could not stay open on Thanksgiving after a competitor complained. Reilly also warned Wal-Mart, Family Dollar and Big Lots not to open, even as many stores across the country got an early start to the holiday shopping season.

Six Boston-area Super 88 Market stores opened up for business Thursday, the Globe reported.

At the Quincy location on Hancock Street, police said they learned at 11:30 a.m. the Super 88 was open for business.

“We sent one officer up there. We told them they had to shut down, and they did,” said Sgt. Agnus McEachern.

But police did not close the four Super 88 stores in Boston, and the Malden store also was allowed to operate, police said.

Super 88 officials reached Thursday told the Globe that Reilly’s warnings were news to them.

“We don’t celebrate” Thanksgiving, said Rudy Chen, a former manager of the Super 88 in Chinatown who now is working as a senior buyer for the chain’s corporate office.

Chen said that the store he managed always was open on Thanksgiving, and that he never had received complaints.