Saudi sisters found dead in Hudson River were in NYC for nearly 2 months, police say Investigators believe the sisters were alive when they entered the Hudson River.

Two sisters from Saudi Arabia whose bodies, bound together with duct tape, were found floating along the Hudson River last week had first arrived in New York City nearly eight weeks prior, a police source told ABC News.

Through mostly electronic evidence, such as credit card transactions and ATM withdrawals, investigators from the New York City Police Department have established that Tala and Rotana Farea traveled from Fairfax, Virginia, where they had previously been living with family since 2015, to Washington, D.C., then to Philadelphia and on to New York City, where they arrived on Sept. 1, the source said.

Detectives are reviewing hotel and restaurant records, surveillance video, electronic statements as well as eyewitness accounts to determine what the sisters were doing and where in the city they were staying between Sept. 1 and Oct. 24, when their bodies were discovered in the Hudson River, the source said.

Investigators believe the women were alive when they entered the water and are checking to see if any surveillance cameras captured that moment. They are also trying to determine whether either of them had met with any counselors or therapists in recent weeks, two police sources told ABC News.

The deaths are being investigated as suspicious and police are equally considering all options, whether they are homicides, suicides or accidents, the sources said.

The medical examiner's office will ultimately determine the causes of death as the investigation continues.

Investigators have also conducted various interviews in Fairfax, Virginia, with family members and other associates of the sisters to learn more about them. Dermot Shea, chief of detectives for the New York City Police Department, said those interviews are "unraveling" what was going on in the sisters' lives before their mysterious deaths.

"I think we've made significant progress in piecing together pieces of this puzzle to find out what happened," Shea said at a press conference Wednesday morning.

"Those interviews are really unraveling, in some way, a piece of the puzzle of behind the scenes," he added. "There is still work to do."

A passerby alerted authorities after spotting the bodies in the Hudson River off of Manhattan's Upper West Side on the afternoon of Oct. 24.

The women were found lying on rocks near the river, fully-clothed, both wearing black jackets with fur trim and black leggings. There were no obvious signs of trauma, police said.

The bodies are believed to have washed ashore with the tide and stayed when the tide went out, police said.

Four days later, police identified the bodies as Tala Farea, 16, and Rotana Farea, 22.

The younger sister, Tala, had been reported missing on Aug. 24, according to the National Center for Missing and Exploited Children. That was the last time the two sisters were seen in Virginia, two police sources told ABC News.

The Royal Consulate General of Saudi Arabia in New York confirmed in a statement Tuesday that the Farea sisters were students accompanying their brother in Washington, D.C.

The consulate said it has "appointed an attorney to follow the case closely" and that authorities "are following closely and constantly for details on the case including the forensic reports showing the causes of death which have not yet been finalized and is still under investigation."

Anyone with information about the Farea sisters is urged to call the New York City Police Department's Crime Stoppers hotline at 1-800-577-TIPS.

ABC News' Kaelyn Forde and Emily Shapiro contributed to this report.