(CNN) -- The deaths within a week of four women -- three of whom had advertised in an adult personals section of a website -- are being treated as the work of one person or group of people, Detroit's police chief said Tuesday.
"At this point, we are working it as one case or one suspect or set of suspects," Chief Ralph L. Godbee told CNN. "There are too many common links for us not to, at this point, work this as one single investigation."
Among those links, he said, is the fact that three of the women had placed online ads dealing with "prearranged adult dating services" and posted on backpage.com, Godbee told reporters Monday.
"We felt it is imperative to alert the public that deciding to meet unknown persons via the Internet can be extremely dangerous," Godbee said.
But a lawyer for backpage.com, Steve Suskin, said it was not clear that his company's website was involved.
"Our team has already provided the police with detailed information about the ads that the suspect or others posted on numerous web sites. Law enforcement authorities now have evidence that the investigation appears to connect to at least 30 different ads or other postings on at least 15 different websites, separate and distinct from ours," Suskin said.
"We are not aware of the existence of any evidence that would indicate which of these many sites were used by the suspect to establish contact with his victims."
The most recent deaths were discovered early Sunday, when police found the bodies of two women, burned beyond recognition, in the trunk of a burning car. The victims have been tentatively identified and are believed to be 28 and 29 years of age, Godbee said. Neither body showed obvious signs of trauma, he said.
Six days earlier, on December 19, the bodies of two other women were found in the trunk of a car parked at a vacant dwelling, Detroit police said.
While autopsy results, including toxicology tests, are not complete, "we are proceeding as if this is two murder scenes," he said.
Backpage representatives have been cooperating with police, who plan to get search warrants and trace computer Internet Protocol addresses and cell phone numbers in an attempt "to start putting this puzzle together," the police chief said.
Postings on the escort section of the website cost $1. Referring to the advertisements on the website as "borderline prostitution," Godbee said that his priorities lie elsewhere. "Right now, we want to get to the bottom of how these four individuals passed away, and who had a hand in their demise," he said.
CNN's Dan Verello contributed to this story.