The murder of a prostitute in a Massachusetts hotel last week has prompted new calls for online classified portal Backpage.com to drop its lucrative and explicit sex ads -- which critics say have been linked to a wide range of crimes around the country.

"As we have seen through our office's work, Backpage.com and the Internet have become increasingly popular vehicles for commercial sexual exploitation," Massachusetts Attorney General Maura Healey said in a statement Tuesday.

"In fact, most of the human trafficking cases that our office has prosecuted specifically involve advertisements on Backpage," Healey said. "It is clear that Backpage must do more to end the kind of exploitation that is advertised every day on its site."

Healey's call for action comes days after Sanisha Johnson, 34, of Bronx, N.Y., was shot to death Thursday inside the Extended Stay Hotel in Burlington by two suspects whom authorities believe preyed on "escorts" listed on Backpage.

Epshod Jeune, 24, of Burlington, and Derrell Fisher, 21, of Boston, were ordered held without bail Monday in the murder, which prosecutors said was part of a scheme to "rob escorts at gunpoint." The pair allegedly used Backpage to rob another prostitute at a separate motel in the area earlier that night.

Witnesses at the Burlington hotel reported hearing screams and a gunshot shortly after midnight Thursday. When authorities entered Room 118, they found Johnson, who was shot once in the chest at close range.

"...Most of the human trafficking cases that our office has prosecuted specifically involve advertisements on Backpage."

- Maura Healey, Massachusetts Attorney General

Like Craigslist, the Dutch-owned Backpage -- which is headquartered in Texas -- has many legitimate advertisements, from apartment rentals to car sales to pet adoptions and job opportunities. But a sizeable portion of advertisements listed within seven categories of the "Adult" section offer money for sex. And many of the listings -- from New York to Texas to California -- are hardly discreet.

"Hey looking for cute petite gal for bj only," writes a 33-year-old male user from Manhattan. 

"Looking for a white/asian gal in need of assistance or fun for a discreet intimate encounter," writes another. "Hopefully you're on birth control."

Under pressure from law enforcement agencies around the country -- including the sheriff of the second-largest county in the U.S. -- Visa announced last month it will no longer process transactions from Backpage.

The decision came shortly after MasterCard ended business with the site in response to pleas from Cook County Sheriff Tom Dart, whose county includes Chicago. 

Authorities with the Cook County Sheriff's Police Department claim to have made hundreds of arrests since 2009 in connection with adult services on Backpage -- from sex trafficking to promoting prostitution.

"(I)nstitutions such as yours have the moral, social and legal right to step up on this pervasive problem and make a fundamental and everlasting difference," Dart wrote in a letter to MasterCard's CEO and board of directors.

According to a 2012 estimate by media research and consulting company AIM Group, Backpage earns more than $22 million each year from prostitution ads. Phone calls and emails to Backpage owner James Larkin were not returned Tuesday. 

"We shouldn't have to wait until law enforcement comes to people's doors," said Eugene O'Donnell, associate professor of crime at John Jay College of Criminal Justice in New York. "It takes a tragedy." 

O'Donnell told FoxNews.com the use of credit cards on the site creates "an aura of legitimacy" and called Backpage a "highway to evil in many respects."

"I think it's clear that women underestimate the risks that are involved," he said. "There’s a dark corner of the web that really has some very dangerous people on there."

O'Donnell said the anonymity of Backpage "multiplies the pool of potential offenders," though he noted electronic transactions create an investigative trail if a crime is later committed.

Such was not the case, however, in 2010 when authorities discovered the bodies of four young women along a stretch of Ocean Parkway on New York's Long Island -- all escorts in their 20's who advertised their services on Craigslist.

Authorities believe the women -- all found wrapped in burlap bags 500 feet apart from each other -- were strangled by the same person or persons. Despite the use of the web in connecting the victims to their killer, the murders remain unsolved. Craigslist since dropped the "escort" service section from its website, which caused prostitutes and pimps to increasingly turn to the pages of Backpage, according to authorities.

A federal law enforcement source told FoxNews.com the Long Island killer was familiar with law enforcement tactics and "went to great lengths to cover up the murders."

"He left no electronic trail," the source said.

Cristina Corbin is a reporter for FoxNews.com. Follow her on Twitter @CristinaCorbin.