By Alexis Tereszcuk - Breaking Celebrity News Entertainment Editor

When Whitney Houston died at the Beverly Hilton Hotel on February 11, it's no surprise that no trace of illegal activity was found, as hotel employees were used to cleaning the singer's room with "extra vigilance" a source tells Breaking Celebrity News exclusively.

Toxicology reports revealed Thursday that Houston had cocaine in her system at the time of death, but according to law enforcement no traces of the illegal drug were found in the room.

February 11th was the last time the 48-year-old pop superstar stayed at the famed hotel, but it wasn't the first time, and Breaking Celebrity News has exclusively learned that after each of her stays hotel staff was instructed to be extra careful and thorough when cleaning her room.

"Beverly Hilton employees had to sweep Whitney's room after every visit and were told to be extra vigilant in their cleaning up," a source tells Breaking Celebrity News.