Investigators have released a photo of a truck that was spotted on surveillance footage in southwest Calgary around the time that Nathan O'Brien and his grandparents disappeared and are looking to speak with the driver.

Kathy and Alvin Liknes and five-year-old Nathan were last seen at 10:00 p.m. Sunday by family memebers.

Police have been at the scene since  Monday and on Friday released images of a truck from CCTV footage collected in the area.

S/Sgt Doug Andrus says the truck was seen several times and police are asking the public for help to find it.

"We have taken steps to try to identify the truck but now we’re asking the public for assistance in identifying the truck and driver. The vehicle was seen in the area the night of the incident driving in the area several times and we believe the person in that vehicle will have information that will assist us in our investigation," said Andrus.

The truck is described as a green, late 80s or early 90s, Ford 150 and police say it appears to have been kept in very good condition. Anyone who saw the vehicle in the area on the night of June 29 is asked to contact police.

Investigators say they have received some forensic results and can confirm that a violent crime occured in the home that night.

"I can’t go into details of what we found in the residence. We’re continuing to assesss this information. I can tell you there was a violent incident in the residence. We’re still assessing the information and we’re hopeful we’ll find these individuals alive," said S/Sgt Andrus.

Police say they spoke to about 75 people at the Parkhill Community Centre on Thursday who attended an estate sale at the home on the weekend.

"We’ve had the family walk through the home and they’ve given us an idea of what has been sold and what should be there. We have a list from yesterday when we met with the invididuals who attended the sale and that has helped us build the list. But the list is incomplete because we haven’t met with everyone at the sale," said Andrus.

40 officers are working on the case and hundreds of tips have poured in from across the country.

"It’s still early in the investigation, we’re only five days in. We’ve done a lot of work but there’s still a lot to be done. We’ve had a lot of support from the public. We have more than 200 tips that we’re going through and that takes time to follow up each tip," said Andrus.

Police say they do not have a motive in the trio's dissappearance and are working on a number of theories.

"We hope to identify the people responsible and hold them accountable and we want to return the family members to their family," said S/Sgt Andrus. We have a number of theories we’ve developed through the course of the investigation and we’re working on those theories and we’ve devoted significant resources to this investigation."

Investigators say there was no indication of forced entry at the home.

Investigators believe more than 200 people were at the estate sale on the weekend and continue to ask anyone who may have attended to contact them through the non-emergency number 403-266-1234 or