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As plans for the weekend funeral of singer Whitney Houston took shape, investigators continued Thursday to look into the singer's prescription drugs and her actions in the days before her death.

Investigators are aware of Houston's partying at the Beverly Hilton in Beverly Hills, California, and other venues "even the night before she died," a source close to the death investigation told CNN's Don Lemon on Thursday.

Hotel personnel have said Houston, 48, was "partying the night before her death in the bar," the source said.

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Investigators are looking at video from Houston's television appearances and other reports as part of the investigation into her physical state and behavior leading up to her death, the source said. Houston died Saturday on the eve of the Grammy Awards.

Hotel surveillance video could reveal Houston's activities in the common areas of the hotel, the source said. The source would not confirm such video exists, but said investigators have requested it.

The anti-anxiety medication Xanax was among prescription drugs found in the room, the source said. Houston's family members and staff confirmed she used the medication, the source said, but investigators don't know whether she took it the day she died. No Valium or other drugs classified as benzodiazepines, or sedatives, were found in the room, according to the source.

Houston also had a prescription for the antibiotic amoxicillin, the source said, but "if taken as prescribed, it's not going to kill you."

Medicine and pill bottles found in Houston's hotel room are currently undergoing basic testing, but nothing so far indicates anything criminal occurred, the source said.

Officials are trying to speed up toxicology testing, the source told CNN.

The source also said any preliminary reporting that family members were told a deadly mixture of alcohol and drugs led to Houston's death is speculative. Investigators do not know what mixture, if any Houston, had in her body.

When paramedics arrived in Houston's hotel suite, she was in the room, not in the bathroom, the source said. "She was lying on the floor, wet, on her back" and had already been removed from the bathtub, according to the source.

"No one official ever saw her in the bathtub or the bathroom," the source said. "The assistant and a bodyguard reported to emergency personnel that Houston was removed from the tub."

Her body was initially discovered by her assistant, Mary Jones, who was often called "Aunt Mary," a family source said earlier this week.

The source said investigators have contacted physicians and pharmacies around the country for information.

The Mickey Fine Pharmacy and Grill in Beverly Hills was one of the pharmacies subpoenaed, the source said. The pharmacy did nothing criminal and is not the focus of the investigation, the source said.

One of the prescriptions found in Houston's suite was from Mickey Fine, according to Ed Winter, assistant chief coroner at the Los Angeles County Coroner's office. But "the prescription that came from Mickey Fine is not something that would kill her," Winter has said.

Mickey Fine is "getting a bad rap from some in the media as if they're the ones doling out prescriptions," the source told CNN. "They're actually the good guys and have been extremely cooperative with the investigation."

Winter has said that while prescription medication was found in Houston's room, the amount was less than that usually present in overdose deaths.

A second source, briefed on Houston's behavior and activity in the days before her death, said she was seen ordering and consuming considerable quantities of alcohol at the hotel two mornings last week.

Houston ordered the drinks before 10 a.m. last Wednesday and Thursday from the bars in the lobby and pool area, the second source said Wednesday. Guests both days overheard Houston loudly complaining about her drinks, accusing bartenders of "watering down" or "putting too much ice" in them, the source said.

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Other guests expressed concern about Houston's erratic behavior, according to the source. Her disheveled appearance, including mismatched clothing, suggested to them that she was intoxicated. The source said Houston was seen jumping in and out of the pool and doing somersaults in the pool area.

Saturday, the day she died, Houston was seen drinking at the pool in the morning, although the source noted witnesses said her behavior did not appear erratic.

Houston's death certificate, filed Wednesday, listed her cause of death as "deferred," meaning a determination is delayed pending more information. Speculation has grown while authorities await the outcome of toxicology tests that could take weeks.

"I know there are reports that she maybe was drowned or did she overdose, but we won't make a final determination until all the tests are in," Winter said earlier. He ruled out foul play and said there were no injuries to Houston's body.

Houston's battles with drug addiction had cast a shadow in recent years over her impressive singing voice and her talent.

However, a close family friend told CNN Tuesday that Houston had not used "hard drugs" for several years, although she was taking medication for a throat infection and Xanax or a similar drug for anxiety and to help her sleep. The friend said Houston was also known to have a drink if she went out.

In Newark, New Jersey, fans left balloons, candles and photographs of the singer in front of the church where her funeral will take place Saturday.

At New Hope Baptist Church, the Newark house of worship where Houston sang as a child, preparations were under way for the private, invitation-only service. Actor Kevin Costner, who starred with Houston in the 1992 hit movie "The Bodyguard," will speak at her funeral, according to a source with knowledge of the funeral plans.

The ceremony will feature performances by Stevie Wonder, Alicia Keys and Aretha Franklin, who is Houston's godmother, a Houston representative said. Singer Roberta Flack will attend, but it was not known Thursday whether she would perform.

Houston's former husband, Bobby Brown will attend and perform later in the day with his group New Edition. Brown considers performing as therapy to get him through a difficult time, a source close to him said.

Samuel DiMaio, Newark police director, told reporters Thursday his advice to fans and curious members of the public was to stay home and watch the ceremony on television, as they will not be able to get close to the church.

The service is expected to be made available for television and web streaming, Houston's publicist said.

A perimeter will be set up for four blocks in two directions, and two blocks in the other directions, DiMaio said. The closest the public will be able to get is a staging area two blocks away.

Although the family is not commenting on Houston's burial location, her death certificate filed Wednesday in Los Angeles lists it as Fairview Cemetery in Westfield, New Jersey.

New Jersey Gov. Chris Christie announced earlier this week that he plans to have the state's flags fly at half-staff on Friday.

Since then, Christie has been standing ground against critics who disagree with his choice to use a tribute typically used to honor fallen soldiers or first responders.

One Twitter user weighed in, "Our flag is to be used to honor true American heroes, the ones you just disrespected."

To that response, Christie seemed to agree to disagree.

"Many in the state are mourning the loss of a cultural icon in NJ's history," he wrote. "We are recognizing her for those contributions."

Educators and Houston friends in East Orange, New Jersey, where Houston attended school. are firm in the their recollections.

"She was a beautiful little girl, very quiet," said Henry Hamilton, who was Houston's principal while she was at Franklin Elementary School. "She was well-respected and never came to the office for discipline problems."

The school is now called the Whitney E. Houston Academy of Creative and Performing Arts.

Childhood friend Erica Taylor said the Houston residence was popular in the summertime: It was the only one to have a built-in swimming pool.

"We would talk about boys and what we were doing over the summer and how it was just fun to be in the pool," said Taylor.