Calgary police are hoping to gather more information about the mysterious disappearance of a five-year-old boy and his grandparents and are asking anyone who purchased items at an estate sale on the weekend to come forward.

Police want to speak to anyone who attended the sale at the home of Alvin and Kathy Liknes on June 28th and 29th and are asking them to bring pictures of items purchased to a special meeting on Thursday at the Parkhill Community Hall from 10 a.m. to 10 p.m.

The Liknes' and their grandson, five-year-old Nathan O’Brien, went missing sometime between 10 p.m. Sunday night and 10 a.m. Monday morning.

Investigators say that the grandparents are not suspects in the disappearance and that evidence collected at the scene suggests they did not leave the home voluntarily.

Nathan's parents and family members made a public appeal on Wednesday for the safe return of their loved ones.

“Nathan. Your mom and dad, Luke and Maximus, and your whole family loves you to every star and back. Nathan, you are our superhero right now and we’re going to bring you home very soon,” said Nathan’s dad Rod.

“Nathan I need you to hear my voice right now and I need you to know that mommy and daddy love you more than anything in this world and we can’t be with you right now but the best people that can be with you other than us is your grandparents and I know grandma’s holding you so tight right now and taking care of you and they are doing everything in their power to keep you safe,” said Nathan’s mother, Jen O’Brien.

Police say dozens of officers are working to bring the family home and over 100 tips have come in from all over the country.

Messages of support for the family are pouring in and a blog has been established for people to post messages.

Calgary's police chief says they are devoting a huge number of resources to the case but they need help from the public.

"We are now convinced that there's people out there that may have information and we've got people assigned to making sure that all tips are prioritized and they're followed up on. We will continue to devote resources to this until it's resolved one way or the other," said Chief Rick Hanson.

CPS S/Sgt Doug Andrus says they have about 40 investigators on the case who are reviewing CCTV footage, following up on tips and conducting an expanded search of the area.

“We’ve had a good response to the appeal. We don’t know how many people attended the estate sale on June 28th and 29th. We’re encouraging anyone who attended the sale and purchased an item to come down to the availability. Bring a picture of that item. Also we’re encouraging anyone who attended the sale but may not have purchased an item to also attend,” said Andrus.

He says they walked family members through the home to see if anything was missing. “That’s why we’re also having people attend here because we want to identify what was purchased and then we can compare to the list of items that may be missing.”

Police say dozens of people were inside the residence for the estate sale and that the meeting on Thursday will help them to eliminate some fingerprints that may have been found at the scene.

"We did do a complete forensic examination of the crime scene including doing fingerprint analysis. There may be people who were there who touched things that we've obtained a print from and it's just a process of elimination," said Andrus.

Andrus says it is still early in the investigation and police are confident they will find the three.

“These people disappeared under suspicious circumstances, we know that, but again we’re keeping an open mind and we’re hoping we find them alive,” said Andrus. “We don’t know if this is a random situation or not. Again we’re keeping an open mind and looking at all possibilities. We don’t know the motive at this point.”

He says they have received some good information and that it has advanced the investigation.

“The media is a big part of this. By getting the word out it encourages people, who have seen or heard something, to contact us. So it’s not only the AMBER Alert, it’s also the media release and the response from the media to get information out there. We can’t do this job alone. We weren’t there. We need the assistance of the public to give us the information,” said Andrus.

Police say the family is struggling and hoping for the best.

“They’re just devastated by this and they’re coping as well as they can. They have a lot of support from family within Calgary and they’ve had family come from outside the city too.’”

Police say they will make investigators available outside of the meeting hours on Thursday for anyone who could not attend and ask they contact them to set up a meeting.

So far there are no suspects but police say they have information that has allowed them to move forward in the investigation.

"We have no suspects that we can name but as I stated we have information that's allowed us to move forward with this investigation," said S/Sgt Andrus.

They have also notified border services, airport authorities and their American counterparts to keep an out for the three.