Police have confirmed they have spoken to her landlord, who reportedly saw her leaving the flat in Clifton, Bristol, with two people.
"We are talking to the landlord and it is a line of inquiry," a force spokesman said.
Chris Jefferies, 65, saw three people leaving the property on 17 December, shortly after 9pm - not long after Miss Yeates, 25, arrived home alone - as he parked his car in Canynge Road.
However, he could not be sure that one of them was Miss Yeates.
Neighbour Liz Lowman, who lives on the opposite side of the street from Miss Yeates's flat with her husband Ray, said Mr Jefferies told her the three people were coming out of an entrance to the mansion house.
"These people were leaving through the communal entrance," she said.
"Unfortunately, we didn't hear or see anything.
"I don't think there was a party that night as I would have heard the music and we heard nothing and we were in all evening."
Avon and Somerset Police have received a good response to their appeal for information following Tuesday's press conference.
• Joanna Yeates: last movements
Yesterday, they were continuing a forensic search of her home, as well as along Longwood Lane in Failand, North Somerset, where her body was found on Christmas Day. Miss Yeates's front door has also been taken away for forensic examination.
Detective Chief Inspector Phil Jones, who is leading the investigation, said: "I am very pleased with the response to our appeals from the press conference yesterday.
"There are a number of lines of inquiry we are following up. One of these concerns apparent reports that several people were seen or heard in or around Joanna's flat on the night of her disappearance. Clearly this is something we are following up.
"As I stated at the media conference yesterday, we know that there were a number of people in the Canynge Road area on the night of Joanna's disappearance. We want to hear from any of these people or anyone else with information that can help the inquiry.
"We have, of course, been keeping in contact with Joanna's family and keeping them informed of our progress. Late last night, I received a message from Mr Yeates in which he stated he and his family had 'total confidence'.
"Indeed, Mr Yeates said: 'We truly believe that you will identify the person who killed our daughter'.I am, of course, grateful to have the support of the family.
"They, and the general public, can rest assured that myself and my team will leave absolutely no stone unturned in our attempts to find whoever killed Joanna and to bring them to justice."
Police have also released CCTV footage of Miss Yeates buying drink from an off-licence on the night she disappeared.
In the short clip, a relaxed-looking Miss Yeates is seen strolling into Bargain Booze in Bristol's Regent Street before buying what is thought to have been a small bottle of cider.
Police released the video in a bid to jog the memories of those who may have seen the murdered woman in the hours leading up to the 25-year-old's disappearance.
Dressed in a white coat with blue jeans, she appears carefree as she approaches the counter.
The landscape architect is then seen looking through her bag before leaving the shop.
Crimestoppers is offering an enhanced reward of 10,000 for information which leads to the arrest and conviction of the person responsible for Miss Yeates's death.