NEW YORK — The search of a New York City basement for possible clues in the disappearance of 6-year-old Etan Patz more than three decades ago has ended, with no human remains found, a source briefed on the investigation told CNN Monday.

Detective Joseph Cavitola, spokesman for the New York Police Department, also said the search was ending. An FBI evidence team, along with police, planned to do another check to be sure nothing was missed.

A field test on what was considered a possible bloodstain found in the basement was negative, the source said. The stain, some possible strands of hair, and a piece of paper will be analyzed at an FBI laboratory in Quantico, Virginia, the source said.

Officials were at the scene Monday, less than 100 yards from Etan’s home. They removed two dumpsters that contained some concrete slabs taken from the basement, which was a carpenter’s workshop at the time Etan vanished May 25, 1979.

The trash bins and their contents were taken to a location to be safeguarded, a source familiar with the investigation said.

Etan’s family still lives in the home where he lived. He would have passed the workshop on the way to the bus stop, which he was walking to alone for the first time when he disappeared.

Days after Etan went missing, the carpenter who worked out of the basement poured a new concrete floor, and it was never dug up until now, according to a law enforcement source.

About a month ago, a cadaver dog reacted to the floor in a way that suggested the possibility of human remains, a law enforcement source said.

The carpenter, Othniel Miller, 75, has not been charged with a crime.

He had no involvement in the disappearance, his lawyer said.

“Mr. Miller has been cooperating with this investigation for over 30 years,” attorney Michael Farkas said Friday. “He has continued to cooperate on multiple occasions. And I am going to assist him in cooperating to the fullest extent possible.”

Miller’s daughter, Stephanie Miller, told CNN affiliate WCBS that her father had cooperated with federal agents, saying he “doesn’t have anything to do with it.”

FBI agents, assisted by the NYPD, discovered the possible bloodstain over the weekend by spraying the chemical luminol, which can indicate the presence of blood, but is not always conclusive, according to a source, who was also briefed on the investigation.

Investigators used chainsaws to dig out the portion of the wall with the stain, which the FBI will analyze to determine whether the substance is blood and, if so, whose it is, one of the sources said. Anything with potential forensic value will be brought to Quantico, two sources said. Analysis could take several days or weeks, one of the sources said.

The search for Etan resumed Monday morning after it was suspended Sunday for what the FBI called “operational reasons.”

Around 2 p.m. Sunday, investigators searching the basement abruptly folded up a tent they had erected to shield them from a nasty rainstorm.

Moments later, two large New York Police Department vans rolled in, obstructing most of the view of the scene. Through a small break between the vehicles, photographers were able to catch a glimpse of something being loaded into the side of an unmarked blue van.

FBI spokesman Peter Donald declined to discuss the reasons behind the search’s suspension. “We’ll be back in the morning,” he said.

Investigators recently relaunched their probe of the cold case, often described as a milestone effort that helped draw the plight of missing children into the national consciousness.

Authorities said both new and old information led them to Miller, a part-time handyman, who met Etan the day before he disappeared and gave him a dollar.

It was interest in Miller that prompted authorities to bring a cadaver dog about 10 days ago to a SoHo basement, where Etan apparently had encountered the carpenter, then 42, a source said.

When agents interviewed Miller about his connection to the basement, the source said Miller blurted out, “What if the body was moved?”

Farkas, the attorney, said he would speak to authorities about that alleged remark.

“I don’t know that he asked that,” Farkas told reporters.

Miller was picked up by the FBI Thursday and was questioned and returned to his Brooklyn apartment, a source said.

In 2010, Manhattan District Attorney Cyrus Vance Jr. said his office decided to take another look at the decades-old mystery. FBI leads were then culled from that case file, sources said.

The investigation garnered national headlines as authorities splashed the child’s image on the sides of milk cartons in the hopes of gathering more information.

Etan was officially declared dead in 2001 as part of a civil lawsuit filed by his family against a drifter, Jose Antonio Ramos, a convicted child molester acquainted with his babysitter.

A judge found Ramos responsible for the death and ordered him to pay the family $2 million. He never paid the money.

Though Ramos has been considered a key focus of the probe for years, he has never been charged in the case. He is serving a 20-year sentence in a Pennsylvania prison for molesting a different boy and is set to be released later this year.

A source said investigators want to expand the pool of possible suspects beyond Ramos.

Stan and Julie Patz, Etan’s parents, wouldn’t comment on the developments. A notice on the apartment building said, “To the hardworking and patient media people: The answer to all your questions at this time is ‘no comment.’ Please stop ringing our bell and calling for interviews.”

SoHo — a Lower Manhattan neighborhood now known for its boutique shops, art galleries and loft apartments — at the time was a grittier locale, where abandoned storefronts dotted the city streets.

The boy’s disappearance raised awareness of child abductions and led to new ways to search for missing children.

President Ronald Reagan named May 25, the day Etan went missing, National Missing Children’s Day.

— CNN’s Susan Candiotti, Deb Feyerick, Ross Levitt, Adam Reiss, and Josh Levs contributed to this report.