Manhattan Murder Mystery Deepens

Construction workers and doormen working at the tony apartment building of murdered celebrity real estate agent Linda Stein submitted to fingerprinting and DNA tests Thursday as police worked feverishly to identify a suspect in this Manhattan murder mystery.

Miguel Chiqui, one of nine construction workers repairing the roof of the Fifth Avenue building in which Stein's body was discovered late Tuesday night, told ABC News that he and the other workmen had been questioned by the police, fingerprinted and had their mouths swabbed for DNA.

He said each of the men signed waivers because "we want to cooperate with police." New York City police declined to comment on the case ABC News calledl them.

Earlier, police said they had no suspects and gave no indication they were any closer to solving the mysterious murder of Stein, 62, known as the "Realtor to the stars," whose client list included Madonna, Sting and Steven Spielberg.

Stein was found in a pool of blood in the living room of her Manhattan apartment night by her daughter Mandy, 34, according to police. There were no signs of forced entry or a struggle.

The building has security cameras at the main and service entrances, doormen and an elevator operator. Police said no murder weapon had been found, and nothing appeared to be missing from the $2.5 million Fifth Avenue flat.

Investigators initially believed Stein had fallen, but Wednesday the New York medical examiner declared the death a homicide.

"She died of blunt-impact injuries to the head and neck," the medical examiner said. Investigators have yet to determine a time of death, but Stein was reportedly still wearing the jogging suit she often donned when walking in nearby Central Park.

A former assistant that was apparently fired from Stein's Prudential Douglas Elliman real estate a firm a few months ago was scheduled to meet with police Thursday night, he told the New York Post. Police sources confirmed to the newspaper that the NYPD is interested in talking to Raul Diaz Bernal, 49, Stein's former assistant. Sources said the two had argued over a sales commission after Bernal accused his boss of stiffing him.

A friend of Stein's told the New York Times that she had been "struggling with a 'distasteful' ex-companion whom she dated about a year ago.'

"She hated him,'' Corcoran broker Liz Spahr told the newspaper on Thursday.

Neighbors who live at 965 Fifth Avenue described the building's security as "excellent."

Outside the service entrance to the building was a large stack of bricks. Police detectives were seen entering the building, as well as private investigators who said they worked for the building were seen outside near the service entrance.

Steve Carroll, a building resident who did not know Stein, said he was "in shock, quite frankly. … Security here is excellent. We've never had any problems like this. That's the thing that has us all scratching our heads. Nobody gets in. There's all kinds of security cameras."

Friends said Stein could at times be "difficult," and local media have reported that Stein had a number of "tumultuous relationships."

Dolly Lenz, vice chairman at Prudential Douglas Elliman Real Estate, who worked with Stein for 20 years, called the real estate agent a "happy lady who had passion about everything she did.

"She could be difficult," Lenz said, "but that was part of her charm."

The Daily News reported Thursday that Stein had reportedly dated a "Latin lover-type last year." According to an anonymous friend of Stein's quoted in the paper, she "dumped the man last year, but he was finding it difficult to 'peel off' and would show up uninvited at her beach house."

Before launching her real estate career, Stein co-managed the seminal punk rock group the Ramones and was for a time married to Seymour Stein, a record executive who signed Madonna.

After divorcing Seymour in the early 1970s, Stein used her celebrity connections to sell real estate. Her first client was Madonna, but her clients also included Billy Joel. Michael Douglas, Calvin Klein and Angelina Jolie.

Elton John and Sylvester Stallone were her friends..

"When she was in the room, she was the queen," Lenz said. "She earned that. It was not something she took. She earned it. She was fabulous -- in the way you have to be born that way to be."