What can a landlord to when a tenant dies in the apartment and next of kin refused to pick up property

Hi, I live in NYC. I am writing to get some information for my parents. Unfortunately, a very nice tenant passed away inside the apartment. She didn't maintain relationships with her family. She only has 1 niece. After the police came to take the body, they sealed the door shut to look for family. They located the niece. The niece said she would pick up the furniture and empty out the apartment. She was told she had to get permission from the city and fill out paperwork. Now, she refuses to do that because she does not want to sign any papers, in case that leaves her liable from any debt from her aunt. So, we are not allowed to unseal the door until she gets authorization. Meanwhile, the apartment is unable to be rented and no one is taking her stuff out. What are my parents rights? They are losing rent monthly, and are not allowed to take the stuff out themselves so they can clear and rent. The niece hung up on my mother yesterday and refuses to have anything to do with the stuff.